Fix mips16 libstdc++ builds. Fix inconsistency from Apr 7 change.

Fix mips16 libstdc++ builds.  Fix inconsistency from Apr 7 change.

	* mips/elf64.h (MAKE_DECL_ONE_ONLY, UNIQUE_SECTION_P): Define.
	* mips/mips.c (mips_select_rtx_section): When TARGET_MIPS16, use
	function_section instead of text_section.
	* mips/mips.h (ENCODE_SECTION_INFO): Add check for UNIQUE_SECTION_P
	in TARGET_MIPS16 STRING_CST handling.

From-SVN: r26824