Add test for nqp::symlink and fix it on the JVM
Add test for nqp::link and fix it on the JVM
This gives us a regex optimizer that can inline simple <?before> and <!before> assertions and also removes some scans that it knows to be useless, like at the beginning of a subcapture or right before a beginning-of-string anchor.
before this patch, it used to ignore single characters, cclasses and erroneously do a range check for ignorecase.
This reverts parts of commit bdbb63a. Apparently $I12 is required to not change its value in here.