RFC: Removing builtin redirects from external headers

[Wilco Dijkstra]

Hi,

Both string/string.h and string/bits/string2.h contain many simple redirects
to builtins. Some are disabled if inlining is turned off, some when optimizations
are disabled, and yet others when either C++ or C is used - ie. there is no
consistency. Are any of these necessary for external headers? 

Would it be reasonable to remove all of the redirects and only add ones that are
used internally in GLIBC (and deemed performance critical) as simple defines in
the internal header include/string.h?

Wilco