toke.c: Call base macro that does the same thing

SPACE_OR_TAB is the same thing as isBLANK, or perhaps more clearly
isBLANK_A.  And these latter macros only have one branch instead of 2
(but some extra masking)
toke.c, S_intuit_method: Minor parsing speedup for 'maybe_method $foo'

This commit moves a scan_word() closer to when it's actually used,
which provides a minor speedup for things like 'new $foo' or
'is $foo, $bar'.
toke.c: VALID_LEN_ONE_IDENT only needs a char, not a char*

Rather than passing s and having the macro do a bunch of *s,
just pass and expect *s.
regcomp.c: Use mnemonic instead of number
Add missing test for regex parse error
lib/utf8.pm: Pod clarification and nit
lib/utf8.pm: Fix pod verbatim line wraps
podcheck.t: Avoid misleading error message

If there are input files on the command line that don't exist, prior to
this commit, the message was output that they are transitory.  This adds
a check and a correct message.
Remove double space between words in pod
charnames: fix nit in comment
utf8.c: Use mnemonics instead of hex numbers
t/porting/bincompat.t: Typo in comment
t/TEST: Don't bail if fails in t/base unless minitest

In order to completely compile Perl, many modules must have been parsed
and compiled, so if there is a full perl, we know that things basically
work.  The purpose of bailing out is that if these supposedly very base
level functionality tests don't work, there's no point in continuing.
But over the years, tests of more esoteric functionality have been
added here, and if one of them doesn't work, it still could be that Perl
pretty much does work.

I believe it would be best to move such non-basic tests elsewhere, but
that's work, and hasn't bitten us much so far; this change lessens the
severity of the biting even more.  Where it will really bite is if
things are so bad that a full perl binary can't be compiled, and we are
trying to figure out why using minitest.
utf8.c: Remove redundant assignment.

This variable is always set just below.
mktables: Fix typos in comments

One of these fixes is for where a real CTRL-X was specified, instead of
$^X
regcomp.c: White-space only, wrap comment to fit
handy.h: Clarify comment
t/porting/regen.t: Add file to check
toke.c: Remove redundant test

This checks that something is both not-printable and not a word
character, but all word characters are printable, so just the
non-printable test suffices.
mg.c: White-space only

I found re-formatting this multi-line 'if' to be easier to understand