gnulib: update to latest
dfa: remove GREP-ifdef'd code in favor of code used by gawk

For many years, gawk and grep have used different #ifdef'd bits of
code relating to how the DFA matcher matches multibyte characters.
Remove the GREP-specific code in favor of the code gawk uses.  This
permits us to avoid still more cases in which grep must resort to
the expensive process of copying/case-converting each input line
before matching against a case-converted regexp.
* src/dfa.c (parse_bracket_exp, atom): As above.
dfasearch: skip kwset optimization when multi-byte+case-insensitive

Now that DFA searching works with multi-byte locales, the only remaining
reason to case-convert the searched input is the kwset optimization.
But multi-byte case-conversion is so expensive that it's not
worthwhile even to attempt that optimization.

* src/dfasearch.c (kwsmusts): Skip this function in ignore-case mode
when the locale is multi-byte.
(EGexecute): Now that this code need not handle multi-byte case-ignoring
matches, remove the expensive copy/case-conversion code.
With no case-converted buffer, there is no longer any need to call
mb_case_map_apply, so remove it and associated code.
(kwsincr_case): Remove function.  Now, every use of this function
is equivalent to a use of kwsincr.  Replace all uses.
* tests/turkish-eyes: Test all of -E, -F and -G.
maint: move two local variable declarations

* src/dfasearch.c (kwsmusts): Move one declaration down to the point
of definition.  Move another into the sole scope where it is used.
maint: remove vestiges of support for long-disabled --mmap option

This option was disabled in March of 2010, and began to elicit a
warning in January of 2012.  Its time has come.
* doc/grep.in.1: Remove mention.
* doc/grep.texi: Likewise.
* src/main.c (GROUP_SEPARATOR_OPTION, usage, MMAP_OPTION)
(long_options, main): Remove all traces.
* tests/Makefile.am (check_PROGRAMS): Remove mention of ignore-mmap.
* tests/ignore-mmap: Remove file.
* NEWS (Maintenance): Mention it.