Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Upgrade of base gcc and libstdc++ to the last GPLv2-licensed revision
(rev. 127959 of gcc-4_2-branch).

Resolved GCC bugs:
c++: 17763, 29365, 30535, 30917, 31337, 31941, 32108, 32112, 32346,
32898, 32992
debug: 32610, 32914
libstdc++: 33084, 33128
middle-end: 32563
rtl-optimization: 33148
tree-optimization: 25413, 32723
target: 32218

Tested by: pointyhat (miwi)
Obtained from: gcc (gcc-4_2-branch up to rev. 127959)
PR: gnu/153298, gnu/153959, gnu/154385
MFC after: 1 month

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