gcc: small merges from upstream
fix ICE in rs6000 when using -fno-trapping-math.
Solves GCC-PR target/30485
Solve GCC issues:
PR middle-end/32602
PR middle-end/32603
Updates the to documentation and processing improvement.
Obtained from: gcc 4.3 (rev. 120902, 120902, 119427, 126278, 126422;
GPLv2)
f881b459a3