* Makefile.in (toplev.o): Depend on diagnostic-color.h.
	* diagnostic-color.c (should_colorize): Remove _WIN32 version.
	(colorize_init): Add argument to _WIN32 version.
	* toplev.c: Include diagnostic-color.h.
	(process_options): Default to -fdiagnostics-color=auto if
	GCC_COLORS env var is in the environment.
	* common.opt (fdiagnostics-color=): Add Var and Init.
	* doc/invoke.texi (-fdiagnostics-color=): Document that if
	GCC_COLORS env var is in the environment, the default is auto
	rather than never.

	* lib/prune.exp: Add -fdiagnostics-color=never to TEST_ALWAYS_FLAGS.
	* lib/c-compat.exp (compat-use-alt-compiler, compat_setup_dfp): Handle
	-fdiagnostics-color=never option similarly to
	-fno-diagnostics-show-caret option.

From-SVN: r198332