3.4/3.5 PATCH: Fix many Solaris 10 g++ testsuite failures

[B. Kosnik]

>> Would we be better off not using int64_t from system headers, but instead
>> via __attribute__((mode("DI"))) or somesuch?
>
>That's for the libstdc++-v3 guys to comment.  Currently, I find both
>constructs: include/bits/postypes.h uses int64_t if available,
>libmath/mathconf.h defines U_int64_t with __attribute ((mode (DI))).  I
>understand that there's some desire to have libstdc++-v3 buildable with
>other compilers, so the use of __attribute__ seems not too desirable.

We prefer to use int64_t from system headers. 

The mathconf.h bits are build-only, and do not end up visible to the end user.

-benjamin