Compilation of language.c in dists will fail if a different version of bison is installed.

Imported from http://bugzilla.roxen.com/bugzilla/show_bug.cgi?id=1505

Reported by @grubba

A pregenerated language.c is supplied in Pike dists. In language.yacc there's a prototype for __yy_memcpy(), which uses a configured value to get the proper type for the last argument. If bison has ben installed on the target platform this configured type may be different from the one in language.c. The file will then fail to compile.

Workaround: Delete the supplied language.c, and let it be regenerated.