query: Add implementation of regex match operator

query: Add implementation of regex match operator

So far this operator was not implemented. This patch adds an additional
value preparation function to the function table for binary operators,
used to compile the regular expression. Unittests are included.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>