If it's made from a dist that should however never happen, as language.h already is generated there. Perhaps you can diff the locally and remotely generated langauge.h and see if it only differs in a few places (or at all).
Ok... Problems seems that I have bison 1.875d...
Tarball language.h is generated by bison 2.0....
Maybe there is some incompatibility with bison 1.8 and 2.0 ?
How can for force Make to NOT generate language.h ?
/Xavier