Clang compiler

To disable a warning (-WWarning) for a portion of code :

• before the portion:

#ifdef CPE_C_CLANG
# pragma clang diagnostic push
# pragma clang diagnostic ignored "-WWarning"
#endif

• after the portion:

#ifdef CPE_C_CLANG
# pragma clang diagnostic pop
#endif

The #ifdef … #endif are some Epeios project related stuff and are not required.