[IMCC] Added code to clear global symbols when running a PIR sub with a pragma at the end of its compilation in IMCC.  This fixes the problem described in RT #60000 (reported by Klass-Jan Stol, where an :immediate sub which uses load_bytecode to load another PIR file often crashes).
[IMCC] Added code to clear global symbols when running a PIR sub with a pragma
at the end of its compilation in IMCC.  This fixes the problem described in RT
#60000 (reported by Klass-Jan Stol, where an :immediate sub which uses
load_bytecode to load another PIR file often crashes).

This is not a beautiful fix; the right approach is to reset the color of all
constant SymRegs stored in IMCC_INFO(interp)->ghash to -1 before running the
immediate subs, but this fixes the problem for now.  Working trumps pretty at
the moment; pretty can come soon.

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@32633 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

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