bug#18454: Improve performance when -P (PCRE) is used in UTF-8 locales

[Norihiro Tanaka]

Thanks for many improvements.  I applied six patches to grep and tried to
compile it, but after the sixth patch, I recevied 'SEEK_DATA' undeclared
error.  I looked for it on CentOS 5.10, but I couldn't find it in standard
header files (glibc 2.5.1) and gnulib files.

==
gcc -std=gnu99 -DHAVE_CONFIG_H -I. -I..  -I../lib -I../lib    -g -O2 -MT
searchutils.o -MD -MP -MF $depbase.Tpo -c -o searchutils.o  searchutils.c && \
mv -f $depbase.Tpo $depbase.Po
grep.c: In function 'fillbuf':
grep.c:718: error: 'SEEK_DATA' undeclared (first use in this function)
grep.c:718: error: (Each undeclared identifier is reported only once
grep.c:718: error: for each function it appears in.)
Makefile:1309: recipe for target 'grep.o' failed
make[2]: *** [grep.o] Error 1
make[2]: *** Waiting for unfinished jobs....
make[2]: Leaving directory '/b/grep-2.20/src'
Makefile:1238: recipe for target 'all-recursive' failed
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory '/b/grep-2.20'
Makefile:1179: recipe for target 'all' failed
make: *** [all] Error 2