[testsuite] add file suffix to scandump messages

[Janis Johnson]

I submitted this back in June but didn't ever check it in:
  http://gcc.gnu.org/ml/gcc-patches/2007-06/msg00834.html

It changes messages from scandump procedures by adding the dump
file suffix and putting the regular expression in quotes.  This
change might have an effect on test result comparisons.  Unless
there are objections I'll check it in tomorrow.  It fixes PR32076.

Janis