Revert "Deprecate literal unescaped "{" in regexes."

This reverts commit 2a53d3314d380af5ab5283758219417c6dfa36e9.

Not the entire commit was reverted, but the deprecation message is
gone.  This caused too many problems.  See thread
http://www.nntp.perl.org/group/perl.perl5.porters/2012/11/msg195425.html
(which lists previous threads).
toke.c: White-space alignment only
smoke