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This incorporates:
2013-09-24 manywarnings: enable nicer gcc warning messages
2013-09-23 warnings: port --enable-gcc-warnings to Solaris Studio 12.3
2013-09-21 timespec: use the new TIMESPEC_RESOLUTION elsewhere
* configure.ac (WERROR_CFLAGS): Omit -fdiagnostics-show-option
and -funit-at-a-time, since manywarnings does that for us now.