Compile in all POSIX class inversion lists

This changes charclass_invlists.h to have the complete definitions for
all the POSIX classes, like \w and [:alpha:].  Thus these won't have to
be loaded off disk at run-time.

Taking advantage of this will be done in stages in future commits
regcomp.c: Rmv code for delayed 'til runtime POSIX defns

The previous commit made compile-time inversion lists available for all
POSIX classes, not just some..  Therefore the code that deals with not
having them available until runtime can be removed.  This commit does
the largest chunk of this code, used when a POSIX class is used within a
bracketed character class.  Later commits will remove more.
regcomp.c: Reword comment to avoid ambiguity
Compile in list of foldable code points

When constructing what matches code points under /i, Perl uses an
inversion list of all the possible code points that participate in
folds.  This number is relatively few compared to the possible universe
of code points, as most of the world's scripts aren't cased, and many
characters in the scripts that do fold aren't foldable (such as
punctuation).  Prior to this commit, the list for the above-Latin1 code
points was read-in from disk if and only if needed.  This commit causes
the list to be added to read-only data in a C header, trading a little
space in Perl's text segment for speed at execution.  This will enable
ripping out some code in this and future commits (offsetting the space
used by this one).
regcomp.c: White-space only

This outdents and reflows lines that were in a block removed in the
previous commit.
Rmv more code for delayed 'til runtime POSIX defns

Now that all the POSIX class definitions are known at compile time, we
no longer need to handle the case that some aren't known until runtime.
This removes some more code that dealt with that.
Remove PL_L1Posix_ptrs

This global array is no longer used, having been removed in previous
commits in this series.

Since it is a global, consideration need be given to possible uses of it
outside the core.  It has never been externally documented, and is an
opaque structure whose internals have changed with every release.  The
functions used to access it are almost all static to regcomp.c; those
few that aren't have been hidden from all but the few .c files that need
to have access to them, via #if's.
regcomp.c: Refactor some code dealing with e.g., [:posix:]

We have a section of code already for handling POSIX classes under /l.
This moves all that handling to there, leading to simpler, easier to
read code, and modifies some comments  Further simplifications will be
in future commits.  We still have to special case [:blank:] on platforms
that don't have isblank().
Keep temp. separate list of foldable characters

When populating what a bracketed character class should match, it turns
out that if we keep a separate list of code points whose folds may have
to be added, we can simplify the code.  This commit just adds the new
list.  Future commits will do the simplification.
regcomp.c: White-space only

This indents code properly that is within a block newly formed by the
previous commit
regcomp.c: Use unconditional match list for POSIX above 255

The POSIX classes, \w, [:blank:], always match the same non-Latin1 code
points regardless of locale, folding, etc.  They can be added to the
unconditional match list, and not have to be dealt with further.
regcomp.c: Collapse two code branches

The previous commit has enabled us to collapse the branches for dealing
with, e.g., \w and \W into the same branch, using a flag to indicate to
complement or not.
regcomp.c: White-space, comments only

This outdents code due to the removal of a block in the previous commit.
And it clarifies some comments about it.
Keep separate list of posix classes and complements

 In building up the list of code points that are matched by a bracketed
 character class, there can be both posix classes and complemented posix
 classes, like [\s\W].  By keeping each type in a separate list, we can
 simplify code in later commits.
regcomp.c: Collapse two code branches

Previous commits have simplified things so these two if-then-else
branches can be collapsed into one.
regcomp.c: Trade a little time for simplicity

Perl currently has two sets of inversion lists for the POSIX classes
built in.  One set is for the entire Unicode range; the other for just
the ASCII range.  This latter set could be derived from the larger one
at run time by doing an intersection with ASCII.  This commit starts the
process of entirely removing the second set, thus avoiding its
bookkeeping.  This commit avoids one use of the ASCII set, instead
adding an intersection with ASCII after all the POSIX classes in a
bracketed character set have been combined.  Thus the penalty is one
intersection per compilation of each bracketed character classes that
contain POSIX classes.
regcomp.c: Collapse two branches.

Previous commits in this series have removed the need to special case
[:ascii:].  This commit removes the special casing.  There is a slight
performance penalty if this is the only POSIX class in the bracketed
class, and is being compiled under /a or /aa: An extra intersection will
be performed.  Since this is regex compilation, this should be
unnoticeable.
regcomp.c: Rmv remaining uses of PL_Posix_ptrs

Previous commits have removed all but a few uses of PL_Posix_ptrs.  This
removes the rest.  ASCII is the same whether over all code points, or
just the ASCII range, so we can substitute the version for all code
points.  There is an extra intersection introduced by this commit during
the construction of a synthetic start class under /a and /aa, but the
performance hit should be negligible.
Rmv PL_Posix_ptrs

Previous commits in this series have removed all uses of this global
array.  This completely removes it.

Since it is a global, consideration need be given to possible uses of it
outside the core.  It has never been externally documented, and is an
opaque structure whose internals have changed with every release.  The
functions used to access it are almost all static to regcomp.c; those
few that aren't have been hidden from all but the few .c files that need
to have access to them, via #if's.
regcomp.c: Reword expression for clarity

I believe the new version is clearer as to what is meant, and it brings
it in line with the same expression in nearby uses.