Update config.sub and config.guess for MIPS R3 and R5 ISA support

Complement commit ae52f483 ("Add MIPS r3 and r5 support.") and get
changes for config.sub to recognize MIPS CPU patterns for the R3 and R5
ISA levels, used by GAS to set defaults in gas/configure.ac.  Oddly, R6
ISA support has been correctly added already.

	/
	* config.guess: Import from upstream.
	* config.sub: Likewise.

	readline/
	* readline/support/config.guess: Import from upstream.
	* readline/support/config.sub: Likewise.