COPYRIGHT: 2014
check return value of nmsg_init()

nmsg_init() returns an nmsg_res, not void. this fixes the following
compiler diagnostic when compiling the cython generated code:

_nmsg.c: In function ‘init_nmsg’:
_nmsg.c:17092:12: warning: ignoring return value of ‘nmsg_init’, declared with attribute warn_unused_result [-Wunused-result]
   nmsg_init();