Replace the egrep findregex() function in find.c to make use of libpcre. Also use libpcreposix, to make all regex.h function calls use the PCRE regex engine. Change all references in display.c from "Egrep" to "PCRE".
The motivation behind this is to give cscope regexes the power of perl's regex language. In particular, non-greedy matches, and character classes such as \d, \w, \s, etc... None of which are supported by egrep. There are many more advantages to using libpcre, over egrep.