When I imported EGCS into contrib/egcs/ I failed to prune out
egcs/gcc/cp/hash.h which is generated from gxx.gperf. Thus `cc1plus' wasn't
using the hash.h we generated by cc/cc_tools/Makefile, but rather the one in
egcs/gcc/cp/.
When I imported contrib/gcc/ I did prune gcc/cp/hash.h. Unfortunately the
GCC maintainers weren't smart on their file nameing and there is also a
egcs/gcc/hash.h (name overloading does NOT work as well on the filesystem
as in C++...). Due to the -I ordering we are were then picking up gcc/hash.h
when compiling `cc1plus'.