op.c: CHANGE_TYPE in Perl_ck_rvconst

Here, op_type and op_ppaddr inits were separated by many lines.
Move them together, then replace with CHANGE_TYPE call.

--
v2- actually remove the explicit op_ppaddr assignment.
Oops in bade9271.
op.c: regularize OP_AELEMFAST_LEX vs OP_AELEMFAST setup.

commit 10884df96723d4 promoted CHANGE_TYPE as the "normal" way to
initialize op_type and op_ppaddr fields.  This suggests that
Perl_rpeep()s tweaking of OP_AELEMFAST and OP_AELEMFAST_LEX is
something of a special case.

It turns out that these are pretty normal too; since regen/opcode.pl
insures that PL_ppaddr[OP_AELEMFAST_LEX] == PL_ppaddr[OP_AELEMFAST],
the invariant: o->op_ppaddr == PL_ppaddr[o->op_type] holds after both
the OP_AELEMFAST and OP_AELEMFAST_LEX branches, and the stronger
semantics of CHANGE_TYPE() can be used to communicate this normality.

On a gcc x86-64 -DEBUGGING build, this enlarges 'size op.o' by 16
bytes, but before and after 'objdump -DS op.o' output suggests that
the code itself is identical.
op.c: CHANGE_TYPE for op_integerize and ck_spair

These 2 callsites alter an OP's type and ppaddr to a closely related
op, by incrementing the op_type, then setting ppaddr, exactly what
CHANGE_TYPE does.

Since CHANGE_TYPE(o, ++type) expands type 2x, it has a problem
with the ++, avoid this using auto vars.