libgo patch committed: Adjust math flags, use them for testing

[Ian Lance Taylor <iant at golang dot org>]

The libgo configury sets special flags to use when compiling the math
package, to get more efficient output.  Unfortunately, it did not use
those flags when testing the math package.  This patch fixes that.
Fixing that revealed that the flags weren't OK for the current math
package, so this patch stops using -funsafe-math-optimizations and
starts using -fno-trapping-math, and makes the options more consistent
across all targets.  This patch also includes
https://golang.org/cl/91335, for the master repo, for better testing
in gccgo for now.  This fixes https://golang.org/issue/23647.
Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu.  Committed
to mainline.

Ian

Attachment: patch.txt
Description: Text document