Fix compilation error appearing on Ubuntu 14.04

The compilation error is:
/home/flahoudere/workset/haka-orig/lib/haka/luadebug/user_remote.c: In function ‘print’:
/home/flahoudere/workset/haka-orig/lib/haka/luadebug/user_remote.c:216:11: error: ignoring return value of ‘vasprintf’, declared with attribute warn_unused_result [-Werror=unused-result]
  vasprintf(&line, format, args);
           ^
/home/flahoudere/workset/haka-orig/lib/haka/luadebug/user_remote.c: In function ‘luadebug_user_remote_server_session’:
/home/flahoudere/workset/haka-orig/lib/haka/luadebug/user_remote.c:357:9: error: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Werror=unused-result]
    write(fd, &command, 1);
         ^
cc1: all warnings being treated as errors
make[2]: *** [lib/haka/CMakeFiles/libhaka.dir/luadebug/user_remote.c.o] Erreur 1
make[1]: *** [lib/haka/CMakeFiles/libhaka.dir/all] Erreur 2
make: *** [all] Erreur 2
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