Inline regcomp.c:S_checkposixcc into its only caller

In the next commit, it will need to access other variables around its
call site.
gv.t: Suppress warning
Stop /[.zog.]/ and /[[.zog.]]/ from leaking

Before croaking, we need to free any SVs we might have allocated tem-
porarily.  Also, Simple_vFAIL does not free the regular expression.
For that we need vFAIL.
Request that regcomp.c:S_regpposixcc be inlined

It is only called from one spot.
utf8.c: Fix a minor refcounting bug caused by 02c8547

Under some circumstances it could cause a hash to point to a freed
element.  But the hash itself was leaking, so it caused on problems,
as no attempt to free its element again was made.

The next commit will stop the hash from leaking.
Stop \P{Assigned} from leaking

I suspect this leak also applies to any large character classes.

An HV created with newHV has a reference count of 1, so doing
newRV_inc on it will cause a leak.
perlhack: Note why some t/op tests avoid test.pl
reduce scope of a var in save_clearsv

svp is a pointer to a pad array slice. It is derefed to set a sv flag.
It's optimized scope previous extended past the savestack_grow call. By
moving the flag setting before any calls in save_clearsv, svp does not have
to be carried across any calls. On some platforms there will be a benefit
(args transfered in vol regs for example, AMD64 Win64), on others none
since it will be reread from the stack after any child call anyway. I
assume the SvPADSTALE_off flag will have no effect on the panic croak.
After this commit, the only auto var carried through a call is
offset_shifted (and unavoidably my_perl).

I saw a drop in the size of save_clearsv from 0x5A to 0x58. The saving
and use of 1 nonvol reg on x86 32 bit VC 2003 was reduced, total stack
frame reduced by 1 pointer, since VC 2003 read svp off the stack only
once at the start of save_clearsv and kept it in a nonvol reg for the rest
of this func's body.
refactor pp_padsv

This commit rearranges the autos in a way to minimize the number of vars
saved across calls. By calculating TARG after EXTEND, TARG does not need
to be saved across a conditional stack grow call. In order to not read
the pad slot and PL_curpad twice (once for TARG, once for save_clearsv),
a * to the pad slot is saved in a volatile. var padentry is calced after
the EXTEND call, but before save_clearsv, and is not saved across
save_clearsv. TARG's scope was not extended to the vifify_ref call, since

1. SP (TOPs assignment) will be referenced anyway after vivify_ref and
this can not be removed.
2. All of pp_padsv has only 3 non-vol inter func vars, my_perl, SP and op.

Adding TARG to remain live past any call (save_clearsv) would add a 4th
non-vol var to this opcode and increase the total stack frame size by
1 pointer, either to save a non-vol reg, or to put TARG directly on the
stack (platform dependent).

The SPAGAIN and RETURN combo was strange, since we fetch global SP, and
then write it right back. But in the old code, the RETURN, if the if branch
is not taken would be required for the XPUSHs. SAVECLEARSV macro included
addr of op, would wouldn't work here, so the func was called directly.
Originally I kept the SAVECLEARSV, but the asm of Visual C showed
recalcing of the pad slot in SAVECLEARSV even though no calls are made in
my revision between EXTEND and SAVECLEARSV, so I forced the compiler to
cache the pad slot. By removing a 2nd PL_curpad dereference, in theory
the CPU can toss a chunk of the pad array from CPU cache away sooner.
TOPs does not inc/dec local SP, so a PUTBACK is not required after
vivify_ref. Brief comments added to explain the unusual code on first
glance. PL_op was cached to remove a couple "*(my_perl+4)"s that were
PL_op being reread after the 2 calls. PL_op caching was the last change I
did. Without PL_op caching, pp_padsv has max 2 cross func saved autos but
was 0x77 long. With PL_op caching, pp_padsv now has 3 saved autos, but is
only 0x72 since some "*(my_perl+4)"s were removed. Since Linux/Win32 32 bit
x86 has only 3 (without ebp) or 4 (with ebp) non-vol regs, this func post
PL_op caching still uses no C stack vars (but nonvol regs are saved and
restored of course). This patch is similar in concept to commit fdf4ddd .

The machine size of pp_padsv dropped from 0x85 to 0x72 for me after this
commit.