[PDB] Fixed debugger segfault when reaching the end of PIR read from the command line; the program counter would walk off the end of the packfile, making the next opcode number very invalid.  Now there's bounds checking at the end of all logical lines of code.
[PDB] Fixed debugger segfault when reaching the end of PIR read from the
command line; the program counter would walk off the end of the packfile,
making the next opcode number very invalid.  Now there's bounds checking at the
end of all logical lines of code.

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@30557 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

parrot/parrot,tewk/parrot-select,parrot/parrot,gitster/parrot,youprofit/parrot,gitster/parrot,tkob/parrot,fernandobrito/parrot,parrot/parrot,fernandobrito/parrot,gagern/parrot,youprofit/parrot,tewk/parrot-select,FROGGS/parrot,tkob/parrot,gitster/parrot,parrot/parrot,tkob/parrot,fernandobrito/parrot,tewk/parrot-select,FROGGS/parrot,tkob/parrot,youprofit/parrot,gagern/parrot,FROGGS/parrot,tewk/parrot-select,fernandobrito/parrot,tewk/parrot-select,youprofit/parrot,fernandobrito/parrot,FROGGS/parrot,gitster/parrot,tewk/parrot-select,tkob/parrot,tkob/parrot,gitster/parrot,gagern/parrot,FROGGS/parrot,youprofit/parrot,tewk/parrot-select,gitster/parrot,tkob/parrot,gagern/parrot,gagern/parrot,gagern/parrot,FROGGS/parrot,FROGGS/parrot,youprofit/parrot,FROGGS/parrot,gitster/parrot,parrot/parrot,gagern/parrot,youprofit/parrot,tkob/parrot,fernandobrito/parrot,fernandobrito/parrot,youprofit/parrot