dfa/MBS_SUPPORT cleanup

[Jim Meyering]

This series removes many #if MBS_SUPPORT guards and
converts many others to "if (MBS_SUPPORT ...", with the
assurance that MBS_SUPPORT is now defined to 0 or 1.

I started this work about 18 months ago and have been carrying
most of these changes since then, rebasing periodically.
I learned the hard way that keeping separable changes in
separate commits makes finding/resolving problems a lot easier.
Several times, a careless rebase ended with one or more of these
changes breaking tests -- and note that all tests now pass both
with and without MBS_SUPPORT.  Also note that the code compiles
and passes "make check" after each of these commits.  Maintaining
that property has been useful.  Otherwise bisection does not work
as well.

Doing this was very tedious, but worthwhile.
With the irritation of the most recent rebase, I passed a
threshold, so have made the effort to polish/complete the series.
I don't want to go through another multi-conflict-inducing rebase ;-)

Most of the early #if-to-"if" conversion commits are mechanical,
and may not look very useful, but some of the more recent commits
actually remove many of the resulting conditionals.  I've found it
easier to see/manipulate expressions when they're all inside if (...)
than when they're split between #if and if (...) expressions.

I'll defer pushing these until tomorrow, in case anyone finds
the time to review/comment.

[01/34] maint: convert #if-MBS_SUPPORT (kwsinit)
[02/34] maint: convert #if-MBS_SUPPORT (Fcompile, etc.)
[03/34] maint: convert #if-MBS_SUPPORT (kwsincr_case)
[04/34] maint: convert #if-MBS_SUPPORT (EGexecute)
[05/34] maint: remove #if-MBS_SUPPORT declaration guards
[06/34] maint: dfa: convert #if-MBS_SUPPORT
[07/34] maint: dfa: convert #if-MBS_SUPPORT (dfafree)
[08/34] maint: dfa: convert #if-MBS_SUPPORT (dfaoptimize,
[09/34] maint: dfa: convert #if-MBS_SUPPORT (free_mbdata)
[10/34] maint: dfa: convert #if-MBS_SUPPORT (dfaexec)
[11/34] maint: dfa: convert #if-MBS_SUPPORT (dfaexec)
[12/34] maint: dfa: convert #if-MBS_SUPPORT
[13/34] maint: dfa: convert #if-MBS_SUPPORT
[14/34] maint: dfa: convert #if-MBS_SUPPORT
[15/34] maint: dfa: convert #if-MBS_SUPPORT (lex)
[16/34] maint: dfa: convert #if-MBS_SUPPORT (copytoks)
[17/34] maint: dfa: convert #if-MBS_SUPPORT (dfaparse)
[18/34] maint: dfa: convert #if-MBS_SUPPORT (state_index)
[19/34] maint: dfa: convert #if-MBS_SUPPORT (dfastate)
[20/34] maint: dfa: convert #if-MBS_SUPPORT (dfastate)
[21/34] maint: dfa: remove some #if MBS_SUPPORT guards
[22/34] maint: ensure that MB_CUR_MAX is defined even when
[23/34] tests: make fmbtest explain (to stderr, not log) why
[24/34] maint: dfa: remove #if MBS_SUPPORT around struct
[25/34] maint: remove #if MBS_SUPPORT around member
[26/34] tests: skip tests that require MBS support
[27/34] build: enable compilation without MBS_SUPPORT
[28/34] maint: dfa: avoid in-function "#if MBS_SUPPORT" tests
[29/34] maint: stop using skip_test_; use skip_ instead
[30/34] maint: dfa: simplify several expressions
[31/34] tests: skip sjis-mb when dfa.c is compiled without MB
[32/34] build: allow compilation once again with ! MBS_SUPPORT
[33/34] maint: dfa: simplify multi-byte-related conditionals
[34/34] maint: dfa: remove case-guarding #if-MBS_SUPPORT