regcomp.c: Rmv no longer called function

regcomp.c: Rmv no longer called function

This hasn't been used since 626725768b7b17463e9ec7b92e2da37105036252
Author: Nicholas Clark <nick@ccl4.org>
 Date:   Thu May 26 22:29:40 2011 -0600

regcomp.c: Fix memory leak regression

 here was a remaining memory leak in the new inversion lists data
structure under threading.  This solves it by changing the
implementation to use a SVpPV instead of doing our own memory
management.  Then the already existing code for handling SVs
returns the memory when done.