don't croak when the \K follows the lookaround assertion

this also simplifies the flagging for these assertions, since this
error is now the only thing using in_lookhead and in_lookbehind they
can be combined into a single in_lookaround.

Rather than conditional increment/decrement as we recurse into S_reg
I simply save the value of in_lookaround and restore it before
returning.  Some unsuccessful or restart paths don't do the restore,
but they either result in a croak(), or a restart which reinitialises
in_lookaround anyway.

Also added tests to ensure that all the different zero-width assertions
with content trigger the error.

(cherry picked from commit 80f44cf4982e395989f886220e05dd2071bb205a)

0 files changed, 0 insertions, 0 deletions