Fixed some compiling errors that appeared on conda with gcc

This fixes #151 (closed) . There were errors of the type:

error: unused variable 'ret' [-Werror=unused-variable]
     void(ret);

And:

LALInferenceHDF5.c: In function 'assert_not_reached':
LALInferenceHDF5.c:41:1: error: 'noreturn' function does return [-Werror]

@leo-singer, this is your code, could you take a look?