SQL/JSON standard defines that jsonpath 'like_regex' predicate should support
the same set of flags as XQuery/XPath.  It appears that implementation of 'q'
flag was missed.  This commit fixes that.

Discussion: https://postgr.es/m/CAPpHfdtyfPsxLYiTjp5Ov8T5xGsB5t3CwE5%2B3PS%3DLLwA%2BxTJog%40mail.gmail.com
Author: Nikita Glukhov, Alexander Korotkov