Remove two compiler warnings:

SWIG/_m2crypto_wrap.c: In function ‘pkey_get_modulus’:
SWIG/_m2crypto_wrap.c:4345: warning: value computed is not used
SWIG/_m2crypto_wrap.c:4370: warning: value computed is not used
SWIG/_m2crypto_wrap.c: At top level:
SWIG/_m2crypto_wrap.c:6118: warning: function declaration isn’t a prototype