There are a couple of files where a C++ style comment characters are used '//'. Unfortunately, while tolerated by gcc, such comments are not legal C and make other compilers balk, for example IBM's XlC stops with an error.
The files concerned are:
lib/ripemd.c: line 59.3
lib/ripemd.c: line 62.3
lib/snefru.c: line 23
Regards Markus