Re-integrate #9138 from maintperl to mainline,

Re-integrate #9138 from maintperl to mainline,
the squelching of the unneeded "Scalars leaked" messages.

p4raw-id: //depot/perl@9203
p4raw-integrated: from //depot/maint-5.6/perl@9202 'copy in'
	t/pragma/strict-vars (@7318..) t/pragma/warn/regcomp (@7887..)
	t/op/regexp.t (@8551..) t/op/lex_assign.t (@8987..) 'merge in'
	t/op/local.t (@5902..) t/pragma/warn/op (@7846..)
	t/pragma/warnings.t (@7895..) t/comp/proto.t (@8173..)
	t/pragma/warn/toke (@8570..) t/op/pat.t (@9076..)