Remove unnecessary mutex, add ecc_fe::is_infty, add ecc_num::set_rnd

[codedust]

No description provided.

[MartKro]

Just removing is dangerous. This is because the specifiers used in the relic library are implementation dependent and therefore the behavior is now undefined (OPENMP also explicitly states that using the directive outside of an #pragma omp is undefined behavior)
#27 goes in a similar direction but also
(1) introduces the PTHREAD MULTI definition such that the __thread specifier is used
(2) the relic mutex now also uses the __thread specifier if the MULTI directive is PTHREAD.
I've researched that __thread is also an specifier for C++0X for certain comilers and commented that the variable should be changed if the code doesn't compile.