[PMC] Plugged a memory leak related to the constant STRING contained in a constant String PMC workaround when thawing said constant String PMC from bytecode.  Hopefully this doesn't make inheriting from the String PMC problematic -- if there are any problems with HLLs and bytecode, this commit is a likely culprit.
[PMC] Plugged a memory leak related to the constant STRING contained in a
constant String PMC workaround when thawing said constant String PMC from
bytecode.  Hopefully this doesn't make inheriting from the String PMC
problematic -- if there are any problems with HLLs and bytecode, this commit is
a likely culprit.

Parrot now leaks no memory for "Hello, world!" written in PIR as well as PBC.

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@39080 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot,ashgti/parrot