Integrate pureperl changes #8844,8845,8850 to mainline

Integrate pureperl changes #8844,8845,8850 to mainline
(via maintperl #8855).

Fixed %^H scoping bug

Removed GV <-> CV refcount loop

Removed %ENV refcount loop

p4raw-link: @8850 on //depot/maint-5.6/pureperl: bae1eca58b94313e4b7677aa241da9fad57bb363
p4raw-link: @8845 on //depot/maint-5.6/pureperl: 4d40626c12bbdd62acfbbe3be104711e58cec2f7
p4raw-link: @8844 on //depot/maint-5.6/pureperl: ea100fc6cfd2f0e23aceb84ac0e804e3c9c3c9a2

p4raw-id: //depot/perl@8858
p4raw-integrated: from //depot/maint-5.6/perl@8857 'merge in' gv.c
	scope.c (@8606..) pp.c (@8635..) op.c (@8758..) perl.c
	(@8806..)