Thanks to Richard Söderberg (coral) /o now works under ithreads and is also tested!
Normally a regex that contains a variable looks like
op_null->op_regcomp->op_match however if /o is specified the first call to op_regcomp changes the optree to op_null->op_match this will never recompile the op. However this is not doable in ithreads, so instead regcomp checks if it should be called or not and returns before it compiles the regex if it has been compiled and /o is specified. This is a bit slower but atleast it works! Also pat.t test 633 and 634 tests /o behaviour!
