error messages - do not repeat class names twice in our error messages

Showing the classname twice in the error message seems friendly when the
class name is short, but when it is long enough that the line wraps the
duplication just increases cognitive load understand the error message.
This is especially the case when the value is a total error and contains
gibberish or a long binary string or such things, something that is all
to common with this type of error. Even with the recently merged eliding
of names the duplication means that an error message can be 2k long in
the worst case, mostly because of the unnecessary duplication.

As a compromise we can simply replace the second invocation of the class
name by saying "it" instead, and that is what this patch does. The error
message is still friendly, but not repetitive. We could also use "the
package" if people preferred.

Thus:
$ perl -le'("x" x 50)->new()'
Can't locate object method "new" via package "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
 (perhaps you forgot to load "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"?) at -e line 1.

Turns into:
$ ./perl -le'("x" x 50)->new()'
Can't locate object method "new" via package "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
 (perhaps you forgot to load it?) at -e line 1.

gv.c

@@ -917,12 +917,11 @@ S_gv_fetchmeth_internal(pTHX_ HV* stash, SV* meth, const char* name, STRLEN len,
                     Perl_ck_warner(aTHX_ packWARN(WARN_SYNTAX),
                         "While trying to resolve method call %.*s->%.*s()"
                         " can not locate package %" SVf_QUOTEDPREFIX " yet it is mentioned in @%.*s::ISA"
-                        " (perhaps you forgot to load %" SVf_QUOTEDPREFIX "?)",
+                        " (perhaps you forgot to load it?)",
                          (int) hvnamelen, hvname,
                          (int) len, name,
                         SVfARG(linear_sv),
-                         (int) hvnamelen, hvname,
-                         SVfARG(linear_sv));
+                         (int) hvnamelen, hvname);
                 }
             }
             continue;
@@ -1263,9 +1262,9 @@ Perl_gv_fetchmethod_pvn_flags(pTHX_ HV *stash, const char *name, const STRLEN le
                 Perl_croak(aTHX_
                            "Can't locate object method %" UTF8f_QUOTEDPREFIX ""
                            " via package %" SVf_QUOTEDPREFIX ""
-                           " (perhaps you forgot to load %" SVf_QUOTEDPREFIX "?)",
+                           " (perhaps you forgot to load it?)",
                            UTF8fARG(is_utf8, name_end - name, name),
-                           SVfARG(packnamesv), SVfARG(packnamesv));
+                           SVfARG(packnamesv));
             }
         }
     }

pod/perldiag.pod

@@ -1169,8 +1169,7 @@ unable to locate this library.  See L<DynaLoader>.
 functioning as a class, but that package doesn't define that particular
 method, nor does any of its base classes.  See L<perlobj>.
 
-=item Can't locate object method "%s" via package "%s" (perhaps you forgot
-to load "%s"?)
+=item Can't locate object method "%s" via package "%s" (perhaps you forgot to load it?)
 
 (F) You called a method on a class that did not exist, and the method
 could not be found in UNIVERSAL.  This often means that a method
@@ -7820,7 +7819,7 @@ can be determined from the template alone.  This is not possible if
 it contains any of the codes @, /, U, u, w or a *-length.  Redesign
 the template.
 
-=item While trying to resolve method call %s->%s() can not locate package "%s" yet it is mentioned in @%s::ISA (perhaps you forgot to load "%s"?)
+=item While trying to resolve method call %s->%s() can not locate package "%s" yet it is mentioned in @%s::ISA (perhaps you forgot to load it?)
 
 (W syntax) It is possible that the C<@ISA> contains a misspelled or never loaded
 package name, which can result in perl choosing an unexpected parent

pp_sys.c

@@ -951,8 +951,8 @@ PP(pp_tie)
                              :                 newSVpvs_flags("main", SVs_TEMP);
                DIE(aTHX_ "Can't locate object method %" PVf_QUOTEDPREFIX
                          " via package %" SVf_QUOTEDPREFIX
-                   " (perhaps you forgot to load %" SVf_QUOTEDPREFIX "?)",
-                   methname, SVfARG(stashname), SVfARG(stashname));
+                   " (perhaps you forgot to load it?)",
+                   methname, SVfARG(stashname));
            }
        }
        else if (!(gv = gv_fetchmethod(stash, methname))) {

t/lib/warnings/gv

@@ -28,7 +28,7 @@ Undefined subroutine &main::joe called at - line 3.
 use warnings 'syntax' ;
 @ISA = qw(Fred); __PACKAGE__->joe()
 EXPECT
-While trying to resolve method call main->joe() can not locate package "Fred" yet it is mentioned in @main::ISA (perhaps you forgot to load "Fred"?) at - line 3.
+While trying to resolve method call main->joe() can not locate package "Fred" yet it is mentioned in @main::ISA (perhaps you forgot to load it?) at - line 3.
 Can't locate object method "joe" via package "main" at - line 3.
 ########
 # gv.c
@@ -57,7 +57,7 @@ $a = bless [], 'C';
 $a->foo();
 __END__
 EXPECT
-While trying to resolve method call C->foo() can not locate package "A" yet it is mentioned in @C::ISA (perhaps you forgot to load "A"?) at - line 18.
+While trying to resolve method call C->foo() can not locate package "A" yet it is mentioned in @C::ISA (perhaps you forgot to load it?) at - line 18.
 I'm in B's foo
 ########
 # gv.c

t/op/tie.t

@@ -930,7 +930,7 @@ sub IO::File::TIEARRAY {
 }
 fileno FOO; tie @a, "FOO"
 EXPECT
-Can't locate object method "TIEARRAY" via package "FOO" (perhaps you forgot to load "FOO"?) at - line 5.
+Can't locate object method "TIEARRAY" via package "FOO" (perhaps you forgot to load it?) at - line 5.
 ########
 # tie into empty package name
 tie $foo, "";

t/run/fresh_perl.t

@@ -81,7 +81,7 @@ $array[128]=1
 ########
 $x=0x0eabcd; print $x->ref;
 EXPECT
-Can't locate object method "ref" via package "961485" (perhaps you forgot to load "961485"?) at - line 1.
+Can't locate object method "ref" via package "961485" (perhaps you forgot to load it?) at - line 1.
 ########
 chop ($str .= <DATA>);
 ########