New regcomp.c build warnings

'make' in blead is now producing the following build warnings:

regcomp.c: In function `Perl_re_compile':
regcomp.c:4390: warning: variable 'exp' might be clobbered by
`longjmp' or `vfork'
regcomp.c:4391: warning: variable 'xend' might be clobbered by
`longjmp' or `vfork'
regcomp.c:4383: warning: argument 'pm_flags' might be clobbered by
`longjmp' or `vfork'

The first two were introduced by:

commit 5b6010b3c3f40e7db51b877d5227c4c80caaa5bb
Author: Yves Orton <demerphq@gmail.com>
Date:   Sat Dec 4 15:26:38 2010 +0100

   make empty string regexp stringify to the same thing regardless of
unicode flags

And the last one comes from:

commit 7b597bb8ab6914a0dfcb8d6fb5c4ca99855e5762
Author: Karl Williamson <public@khwilliamson.com>
Date:   Fri Dec 3 08:54:37 2010 -0700

    regcomp.c: Move code out of longjump area

    This code should be done before the setjump to avoid the longjump
    clobbering it.

• New regcomp.c build warnings by Jerry D. Hedden