Avoid overly-greedy match in dejagnu regexp.

Avoid overly-greedy match in dejagnu regexp.

Occasionally I've been seeing failures with the multi-line diagnostics.  It's never been clear what's causing the spurious failures, though I have long suspected a greedy regexp match.

It happened again yesterday with a local change that in no way should affect diagnostics, so I finally went searching and found that sure enough the multi-line diagnostics had a ".*" in their regexp.  According to the comments, the .* is primarily to catch any dg directives that may appear -- ie it should eat to EOL, but not multiple lines.  But a .* can indeed match a newline and cause it to eat multiple lines.

The fix is simple.  [^\r\n]* will eat to EOL, but not further.

Regression tested on x86_64 and on our internal target.

gcc/testsuite

	* lib/multiline.exp (_build_multiline_regex): Use a better
	regexp than .* to match up to EOL.