Attempt at getting sigspacing right
Try to do sigspace better in NQP::Grammar
Do sigspace even more right

Now only finds sigspace after an allowed metachar
Small fixes to sigspace
Replace sigspace in NQPGrammar so we can bootstrap
Bootstrap sigspace and get up to make
Panic after a null regexes ( RT #77784 )

Now catches and dies on more (hopefully all) null regexes, un-terminated
regexes, and unrecognized metacharacters
Replace <.throw_null_pattern> on regex infixes
Don't grab sigspace after $<var> = binding
Remove hard-to-reach debugging lines
Make sigspace after $<var> = binding significant

Doing this required complexifying the grammar some, but in the process I
was at least able to simplify the $<quantified_atom> action
Get tests up to spec
Update bootstrap files with STD-compliant sigspace

Only Parrot and JVM. I cannot currently build NQP on MoarVM, but should
anyone else be willing generate the bootstrap files for it (and please
do), the basic process is:

    git checkout 3b73abb0c src/NQP/Grammar.nqp
    make bootstrap-files
    git checkout -- .

Otherwise, solves GH #140
Merge branch 'master' into stdsigspace
Fixes to work correctly on Rakudo
Merge branch 'master' of https://github.com/perl6/nqp into stdsigspace
Merge branch 'master' of https://github.com/perl6/nqp into stdsigspace
Update MoarVM bootstrap
Merge branch 'stdsigspace' of https://github.com/perl6/nqp