Some simple, uncommentable Cursor tracking.
Create a per-grammar fail Cursor.

This is used in various places to make failure allocate less. Attached
to ParseShared to still get type correct.

The places it's used so far takes NQP.nqp from creating 284742 Cursor
objects in its parse to 229535, though needs more testing.
Used shared fail Curosr in some HLL::Grammar rules

Shaves another 15,000 Cursor creations off when compiling NQP.nqp.
Together with the previous change, that's 25% of Cursor allocations
vanished for this case.
Turn some <?before ...> into simpler constructs.

In NQP::Grammar; saves 1000 Cursor allocations in NQP.nqp parse.
Only hit quote_escape:sym<misc> if there's a \\.

This means the LTM analysis can eliminate 15,000 calls to this rule
while parsing NQP.nqp.
Some <before...> simplification in P6Regex grammar

There's a few other places we could in theory do it, but they break
tests, it seems. This one is the big win, anyway.
Fix typo
make backslash:misc an enumcharlist

So <?[\]]> will actually have zerowidth.
proper handling of classes an zerowidth

jnthn++, I am just his commitbot :o)
Fix a couple of bits of busted syntax in tests.

This was OK before, but is not valid Perl 6 and we get caught out when
ident LTMs properly.
Prevent sigspace leakage.

Won't be needed after sigspace changes to get up to latest spec are
done.
Re-order for correct LTM tie-break.
Treat ident declaratively.

timotimo++ and diakopter++
Save a ton of CURSOR allocations in MARKER.
proper handling of classes an zerowidth, jnthn++
Build simpler QAST for some cclasses.

This brings a bunch more into the realm of what the NFA builder can
handle (probably it should cope with yet more, but this fixes the
LTM for the Perl 6 grammar's apostrophe token, which is a big win).