igprof_analyse -mr REGEXP option activated if libpcre can be found.

EDIT: die function after pcre_compile was not printing anything.
      Replaced it with std::cerr << Error... call and exit(1);

      in replace function replace.clear() to clear the replace string
      which fix the bug when there were more than one regexp
Merge pull request #27 from mkurkela/mergebyregexp_fix

igprof-analyse -mr REGEXP option activated if libpcre can be found.