[testsuite] scandump.exp: use printable version of regexp

[Mike Stump]

On Jun 13, 2012, at 2:13 PM, Janis Johnson wrote:
> Most scan-* procedures used in dg-final test directives use a printable
> version of the regular expression in the test summary.  This patch makes
> scan-*-dump-tiles do that as well, which eliminates several duplicates
> in test summaries for expressions that contain a newline.

Ok.