t/re/charset.t: Better test descriptions
pod/perlrecharclass: Nits
pod/perlrecharclass: Document [:blank:], [:ascii:] for C89 platforms

These POSIX classes were introduced in C99, and not all C89 platforms
recognize them.  The behavior there was previously undocumented
regcomp.c: Add some comments
perlfunc: 'if' is in perlsyn, not perlop

Thanks to Hauke D for pointing this out.
lib/B/Deparse.t: TODO test for [perl #120950]

This moves a test to earlier in the file where it now fails, and makes
it TODO.  It also creates a copy just after the failure, this time
without the TODO, to show that it is order dependent.

This is in preparation for some commits that exposed this bug.
utf8.c: Add comment
regexec.c: White-space only

Align a macro continuation backslash
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.