Dependency on outdated PCRE3 library

[humenda]

Pplatex depends on the old, obsolete PCRE3 library (i.e.
It has been end of life for a while now, and upstream do not intend to fix any
further bugs in it.
In particular, Debian intends to remove the library from its distribution,
resulting also in the removal of pplatex (would also affect Ubuntu and
derivatives).

Could pplatex please be ported to the more up-to-date version, documented here:
https://pcre.org/current/doc/html/

For completeness, here is the Debian bug:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1070288

Thanks!