[testsuite] Enable column location checking for 'dg-optimized', 'dg-missed'

[testsuite] Enable column location checking for 'dg-optimized', 'dg-missed'

'process-message' would like the 'msgprefix' argument without trailing space.

This is a small bug-fix for commit ed2d9d3720adef3a260b8a55e17e744352a901fc
"dumpfile.c: use prefixes other than 'note: ' for
MSG_{OPTIMIZED_LOCATIONS|MISSED_OPTIMIZATION}", which added 'dg-optimized',
'dg-missed'.

	gcc/testsuite/
	* lib/gcc-dg.exp (dg-optimized, dg-missed): Fix 'process-message'
	call.
	* gcc.dg/vect/nodump-vect-opt-info-1.c: Demonstrate.
	* gcc.dg/vect/nodump-vect-opt-info-2.c: Likewise.