regmatch(): consolidate locinput++

regmatch(): consolidate locinput++

There are several places in the code that increment locinput by 1 char
(which may or may not be 1 byte) then update nextchr.

Consolidate these into a single code block with the others goto'ing it.
This actually reduces the code more than it appears, since the CCC_TRY*
macros expand into several branches, each of which repeatthe
increment code.