Add regex/2,3 predicate

regex/3 predicate takes a pattern term in the form of a regular
expression and either a single term or a list of terms to match the
pattern against. Returns each match.

regex/2 predicate takes the pattern and term(s) to match and returns
true if any match exists.

Change-Id: I20e18a84ea22f9c508aac9beb3136798b9c88eee