Don't trip up over strings in QAST nodes.
Don't trip up over strings in QAST nodes.

It's locallifetime that led to the observable explosion, but handle
has been around and this code was vulnerable to that also. Fixes the
macro test regressions in Rakudo.

cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp,cygx/nqp