_dirtyforms_match_rules incorrectly converts strings into regexes (problem with hyphens)

This might have worked in previous versions of PHP but it doesn't anymore:
For instance, the expression *-translation-table-* is converted into:
.*[-[-_]]translation[-[-_]]table[-[-_]].*
instead of the expected:
.*[-_]translation[-_]table[-_].*
Thus preventing form ID to be matched.

The attached patch fixes this issue.