support using the PCRE JIT
Submitted by Christian Persch
Link to original bug (#679155)
Latest PCRE supports JIT code generation to speed up matching (at the expense of slower g_regex_new()).
See http://sljit.sourceforge.net/pcre.html and http://sljit.sourceforge.net/regex_perf.html for some data on the performance of JITing vs. the interpreter.
Pushed a proposal to the wip/pcre-jit branch.