regcomp.c: Move some statements

These statements are moved to after the debugging code so that the two
functions are essentially identical before them.  This will allow the
two to be combined in a future commit.  I verified by testing that the
debugging info was not affected.
regcomp.c: Extract duplicated code to fcn

This causes the nearly-duplicate code of S_reg_node and S_reganode to be
placed into a single function, S_regnode_guts.

There is one place where it might not be obvious that this doesn't
change things.  And that is under DEBUGGING, reg_node() called

    Set_Node_Offset(RExC_emit, RExC_parse + (op == END));

and reganode called

    Set_Cur_Node_Offset;

However Set_Cur_Node_Offset is defined to be

    Set_Node_Offset(RExC_emit, RExC_parse)

and since op will never be END for reganode, the two statements are
equivalent.
regcomp.h: Use existing macro instead of reinventing
regcomp.h: Remove obsolete #defines

These internal definitions are no longer used.
regcomp.c: Outdent line to align with neighbors
regcomp.h: Add comment
regcomp.sym: ANYOF nodes have an argument

Plus a bitmap, but they always have an argument besides, contrary to
what was specified here.  Future commits rely on this, whereas
heretofore this error was harmless.
regcomp.c: Add a function and use it

This adds a function to allocate a regnode with 2 32-bit arguments, and
uses it, rather than the ad-hoc code that did the same thing previously.
This is in preparation for this code being used in a 2nd place in a
future commit.
regcomp.c: Add assertions

This changes from assuming that certain things are constant to using a
variable instead, and then asserting that the variable matches the
constant.
Up regex flags limit for (??{})

Previously the regex pattern compilation flags needed for this construct
would fit into an 8-bit byte.  This conveniently fits into the flags
structure element of a regnode.  There are changes coming that require
more than 8 bits, so in preparation, this commit adds an argument to the
node that implements (??{}) (31-bits usable for flags), and moves the
storage to that.
op_reg_common.h: #define in terms of more basic one

The mask to copy bits should always include at least the compile-time
bits.  By defining it in terms of the compile-time bits, we make it
easier to change and understand.
Make space for /xx flag

This doesn't actually use the flag yet.
We no longer have to make version-dependent changes to
ext/Devel-Peek/t/Peek.t, (it being in /ext) so this doesn't
op_reg_common.h: White-space only

Align columns vertically
toke.c: Clarify comment
Deprecate multiple "x" in "/xx"

 It is planned for a future Perl release to have /xx mean something
 different from just /x.  To prepare for this, this commit raises a
 deprecation warning if someone currently has this usage.  A grep of CPAN
 did not turn up any instances of this, but this is to be safe anyway.

 The added code is more general than actually needed, in case we want to
 do this for another flag.
B/Makefile.PL: Allow constants to be long/unsigned

This looks for numerical constants, but failed to see long and/or
unsigned ones, which have suffixes U and/or L, or lowercase u and/or l.
op_reg_common.h: Update comment

The PL file previously referred to has been deleted, and replaced by a
different one.
Suppress some Solaris warnings

We get an integer overflow message when we left shift a 1 into the
highest bit of a word.  This changes the 1's into 1U's to indicate
unsigned.  This is done for all the flag bits in the affected word, as
they could get reorderd by someone in the future, unintentionally
reintroducing this problem again.
regcomp.c: Properly dereference a ptr

UTF8_IS_INVARIANT takes a byte as its argument, not a ptr.  This bug was
introduced by 62a59291 in 5.21.4.  It doesn't probably cause bugs
because the ptr is always too big to be an invariant, but it slows
things down somewhat by not taking a shortcut it could.

It turns out that there is a discrepency between the APIs of the
UTF8-foo macros.  Some take a byte, and some a string ptr.
Eliminate unused BACK regnode