* config.gcc (all_defaults): Add arch_32 arch_64 cpu_32 cpu_64
	tune_32 tune_64.
	(i[34567]86-*-* | x86_64-*-*): Add arch_32 arch_64 cpu_32 cpu_64
	tune_32 tune_64 to supported_defaults.  Allow values not
	supporting 64-bit mode for arch_32, cpu_32 and tune_32 for
	x86_64.  Do not override cpu_32 or cpu_64 values from target name.
	(i[34567]86-*-linux*, i[34567]86-*-solaris2.1[0-9]*): Only default
	with_cpu_64 to generic for 64-bit-supporting configurations, not
	with_cpu.  Remove FIXMEs.
	* doc/install.texi (--with-cpu-32, --with-cpu-64, --with-arch-32,
	--with-arch-64, --with-tune-32, --with-tune-64): Document.
	* config/i386/i386.h (OPT_ARCH32, OPT_ARCH64): Define.
	(OPTION_DEFAULT_SPECS): Add tune_32, tune_64, cpu_32, cpu_64,
	arch_32 and arch_64.

From-SVN: r136674