Add comment about why "skip global checks" is turned on

intl.emu

@@ -46,8 +46,8 @@
           ): either a normal completion containing an Intl mathematical value or a throw completion
         </h1>
         <dl class="header">
-          <dt>skip global checks</dt>
-          <dd>true</dd>
+          <dt>skip global checks</dt> <!-- this can be presumably deleted when merged in to 402. It it present only because ecmarkup complains about the totality of ToIntlMathematicalValue. Here's what ecmarkup says: -->
+          <dd>true</dd> <!-- warning: every call site of ToIntlMathematicalValue asserts the return value is a normal completion; it should be refactored to not return a completion record at all. if this AO is called in ways ecmarkup cannot analyze, add the "skip global checks" attribute to the header (always-asserted-normal) at intl.emu:46:7: -->
           <dt>description</dt>
           <dd>
             It returns _value_ converted to an <dfn id="intl-mathematical-value">Intl mathematical value</dfn>, which is either a mathematical value<ins> a finite Decimal128 value,</ins> or one of ~positive-infinity~, ~negative-infinity~, ~not-a-number~, and ~negative-zero~.