Add consistent synonyms for \p{PosxFOO}

Add consistent synonyms for \p{PosxFOO}

This patch adds a set of synonyms \p{XPosixFOO} for the full extended
Unicode version of \p{PosixFOO}, so only one rule need be remembered.
Similarly, \p{XPerlSpace} is added to preserve the rule for the one
similar class that doesn't have Posix in its name.

Prior to this patch there was no exact equivalent to \p{PosixPunct}
extended beyond ASCII.