Makefile: promote wildmatch to be the default fnmatch implementation

This makes git use wildmatch by default for all fnmatch() calls. Users
who want to use system fnmatch (or compat fnmatch) need to set
NO_WILDMATCH flag.

wildmatch is a drop-in fnmatch replacement with more features. Using
wildmatch gives us a consistent behavior across platforms. The
tentative plan is make it default with an opt-out for about 2 cycles,
then remove NO_WILDMATCH and compat/fnmatch.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -106,7 +106,7 @@ all::
 # Define NO_FNMATCH_CASEFOLD if your fnmatch function doesn't have the
 # FNM_CASEFOLD GNU extension.
 #
-# Define USE_WILDMATCH if you want to use Git's wildmatch
+# Define NO_WILDMATCH if you do not want to use Git's wildmatch
 # implementation as fnmatch
 #
 # Define NO_GECOS_IN_PWENT if you don't have pw_gecos in struct passwd
@@ -1261,7 +1261,7 @@ ifdef NO_FNMATCH_CASEFOLD
 	COMPAT_OBJS += compat/fnmatch/fnmatch.o
 endif
 endif
-ifdef USE_WILDMATCH
+ifndef NO_WILDMATCH
 	COMPAT_CFLAGS += -DUSE_WILDMATCH
 endif
 ifdef NO_SETENV