Fix to regex op compiler.
Fixes to dynamic variable handling.

Brings things inline with other backends, fixing the bug affecting
32-protoregex.t.
missing write barriers and more standard write barriers
more missing write barriers
The arg buffer must be walked during GC.

Failure to do so means that any parameter binding process that causes
allocations could end up pulling things out of an args buffer full of
old pointers.
Fix container configuration storage.

Keep the key string around, so the hash won't point off into random
memory.
Positional/associative delegate v P6opaque.compose

The usage in QASTNode worked as it came from object serialized in the
cross-compile. Needed handling of these in compose for it to work in
selfhost, though. Fixes 73-delegation.t.
Don't forget to copy bytecode_size.

Need to further review what MVMStaticFrame.copy_to is doing, but this
gets 56-role.t a little further.
the rest of the nqp test (7 of them).. we pass a few of them already
implemented compunitcodes op
moved ContainerRegistry to instance
implemented getcodecuid op
added missing getcodecuid op
avoids a MVMROOT
import more constants from jvm-backend
removed a bunch of MVMROOT
removed another pieces of MVMROOT
bring nqp::readlinefh in line with jvm/parrot

That is, read and return trailing newlines.
use CREDITS file from nqp for testing
Revert "removed another pieces of MVMROOT"

This reverts commit b4aaa4a913b83b96261d52f4509c2ddacf38ac54.