Use optimized implementation of mb_strcut for Japanese mobile vendor UTF-8 variants

To facilitate sharing of mb_cut_utf8, I combined mbfilter_utf8.c and
mbfilter_utf8_mobile.c into a single source file.

Author: alexdowad

ext/mbstring/config.m4

@@ -106,7 +106,6 @@ AC_DEFUN([PHP_MBSTRING_SETUP_LIBMBFL], [
     libmbfl/filters/mbfilter_utf7.c
     libmbfl/filters/mbfilter_utf7imap.c
     libmbfl/filters/mbfilter_utf8.c
-    libmbfl/filters/mbfilter_utf8_mobile.c
     libmbfl/filters/mbfilter_uuencode.c
     libmbfl/mbfl/mbfilter.c
     libmbfl/mbfl/mbfilter_8bit.c

ext/mbstring/config.w32

@@ -22,7 +22,7 @@ if (PHP_MBSTRING != "no") {
 			mbfilter_qprint.c mbfilter_ucs2.c \
 			mbfilter_ucs4.c mbfilter_utf16.c mbfilter_utf32.c \
 			mbfilter_utf7.c mbfilter_utf7imap.c mbfilter_utf8.c \
-			mbfilter_utf8_mobile.c mbfilter_uuencode.c \
+			mbfilter_uuencode.c \
 			mbfilter_singlebyte.c", "mbstring");
 
 		ADD_SOURCES("ext/mbstring/libmbfl/mbfl", "mbfilter.c mbfilter_8bit.c \