re PR target/65296 ([avr] fix various issues with specs file generation)

re PR target/65296 ([avr] fix various issues with specs file generation)

gcc/
	PR target/65296
	* configure.ac [avr]: Check as for options -mrmw, --mlink-relax.
	* configure: Regenerate.
	* config.in: Regenerate.
	* doc/invoke.texi (AVR Options) [-mrmw]: Document it.
	[-mn-flash]: Document it.
	[__AVR_ARCH__]: Document avrtiny.
	* config/avr/gen-avr-mmcu-specs.c (config.h): Include it.
	(*asm_relax): Only define spec if HAVE_AS_AVR_MLINK_RELAX_OPTION.
	(*asm_rmw): Only define spec if HAVE_AS_AVR_MRMW_OPTION.
gcc/testsuite/
	PR target/65296
	* gcc.target/avr/tiny-memx: Use -mmcu instead of -march.
	* gcc.target/avr/tiny-caller-save.c: Same.

From-SVN: r221355