Use @acronym{MIPS} where appropriate.

Use @acronym{MIPS} where appropriate.
See http://sourceware.org/ml/gdb-patches/2012-04/threads.html#01091 and
http://sourceware.org/ml/gdb-patches/2012-05/threads.html#00731 for the
related discussions.

	* gdb.texinfo (Continuing and Stepping, Selection, Byte Order)
	(MIPS Embedded, MIPS, MIPS Register packet Format)
	(Target Descriptions, MIPS Features): Use @acronym{MIPS} where
	appropriate.