unicode_constants.pl: Consider all \pP for delims

unicode_constants.pl: Consider all \pP for delims

Previously, only the punctuation characters that Unicode had classed as
being opening/closing were considered in looking for suitable paired
delimiters.

This commit looks at all punctuation characters.  There are actually
only 7 new pairs found.

This gives us ꧁      ꧂   as string delimiterss, if your font allows,
which are Javanese and used to surround an honorific title, according to
Wikipedia.