perlop: Add note about (?[])
regcomp.c: Slight optimization

A swash is accessed either through its inversion list or its hash (only
large swashes actually have hashes; this is usually transparent).  At
this point in regcomp.c, we only will be looking at the inversion list;
by telling swash_init function that via the flag, later accesses
automatically have a level of indirection removed.
doio.c: Remove EBCDIC dependency

For non-EBCDIC this file used \012 instead of \n.  This may have been a
MAC OS Classic hack, which we no longer support.
perlapi: May want to use savesharedpv on threaded Win32

Adds a note to savepv (and similar) that on threaded Windows
that you may need to use the saveshared version because the memory is
deallocated when the thread ends.
Fix broken locale case-insensitive matching

Commit 68067e4e501e2ae1c0fb44558b6aa5c0a80a4143 inadvertently
broke regular expression /i matching under locale.  The tests for this
were defective, so the breakage was not caught.  A later commit will fix
the tests, but this commit restores the functionality.

It also casts the input parameter to some functions to be U8 to make
sure that optimizing compilers can omit bounds checks
utf8.c: Use U8 instead of UV in several places

These temporaries are all known to fit into 8 bits; by using a U8 it
should be more obvious to an optimizing compiler, and so the bounds
checking need not be done.
lib/locale.t: Shorten function name

This is just so that future commits won't have to wrap so many lines to
fit in 79 columns
lib/locale.t: Add debug verbosity level

Several prints were commented out (by using an 'if 0').  Instead convert
them to use the function that displays characters using only ASCII
printables, and subject to output when the PERL_DEBUG_FULL_TEST is more
than 1.
lib/locale.t: Add some debugging info
lib/locale.t: Use lexical instead of $_ in a block

This is because $_ will be used in a future commit for something else
lib/locale.t: Make another test TODO if it fails

Many platforms have a few locales whose casing functionality is buggy.
However if only a few locales have failures, it probably means that Perl
is ok; and its the platform's locale definitions that are bad.  Earlier,
commit 6d5d702a337e9161f8eb85180a83c4469a8f7ed7 enhanced locale.t, if
only a few locales fail, to mark some tests which were showing these
kinds of bugs as TODOs.  This allowed robust tests to be added to
locale.t which previously were ommitted so as to not cause the tests to
fail if any locale on any platform was bad.  Not having these tests
allowed real Perl bugs to creep in.

This commit adds the /il match testing to the list of these tests.
Currently, it is set to hardly catch anything; and this allowed
another real bug to be introduced into Perl.

This commit was prompted by bugs in Darwin with ISO8859-4 and ISO8859-13
locales.
lib/locale.t: Test /il matching

Case-insensitive matching was essentially being skipped here.  This was
because some locales were broken on some platforms which caused locale.t
to always fail somewhere.  However, the previous commit has changed that
so if just a few locales are bad, the tests are marked as TODOs.  Thus
we can make the /il match tests robust.