invoke.texi: Add -mlong32 documentation.

invoke.texi: Add -mlong32 documentation.

	* invoke.texi: Add -mlong32 documentation.
	* config/mips/mips.h (mips_explicit_type_size_string): New.
	(TARGET_SWITCHES): Add 'long32'.
	(TARGET_OPTIONS): Add 'explicit-type-size'.
	(CC1_SPECS): Set -mexplicit-type-size.
        (LONG_MAX_SPEC): Change a use of 'no-long64' to 'long32'.
	* config/mips/abi64.h (LONG_MAX_SPEC): Same.  Add 'mabi=32'.
	* config/mips/mips.c (mips_explicit_type_size_string): New.
	(override_options): Use it.
	* config/mips/osfrose.h (CC1_SPECS): Set -mexplicit-type-size.
	* config/mips/mips.h (SUBTARGET_CPP_SIZE_SPEC):
	Pointer size now depends on both size longs and size of GP
	registers.

From-SVN: r25799