[PMC] Fixed Env PMC, which mistakenly returned CONST_STRING-created strings to its caller.  You can't do this, lest other code modify the constant string in place, and things go kablooie elsewhere.  Arguably, CONST_STRING should avoid this problem, but for now, Env PMC now returns fresh empty strings for calling code to mangle as it sees fit.  Weird segfaults in the string subsystem averted.  See RT #57120, filed by Reini Urban, for one symptom.
[PMC] Fixed Env PMC, which mistakenly returned CONST_STRING-created strings to
its caller.  You can't do this, lest other code modify the constant string in
place, and things go kablooie elsewhere.  Arguably, CONST_STRING should avoid
this problem, but for now, Env PMC now returns fresh empty strings for calling
code to mangle as it sees fit.  Weird segfaults in the string subsystem
averted.  See RT #57120, filed by Reini Urban, for one symptom.

git-svn-id: 6e74a02f85675cec270f5d931b0f6998666294a3@31936 d31e2699-5ff4-0310-a27c-f18f2fbe73fe

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