Add typevar scope handling for MoarVM.

Uses op that indicates that the value is invariant with regards to the
invocant type.
On Parrot and JVM, for now typevar means lexical.
Start marking $?CLASS lookup with typevar scope.
One more place we can use typevar, not lexical.

This benefits !cursor_start, meaning that all the attribute accesses
in it are now lowered to pointer operations. Le JIT will like this -
once it can handle other things inside !cursor_start, anyway.
Merge branch 'typevaropt'
Bump MOAR_REVISION for inline/deopt fixes.