Revert a change that breaks (at least) all "max" builds.

mysys/Makefile.am:
  Revert a change that breaks (at least) all "max" builds: "mf_keycache.o" is needed.

mysys/Makefile.am

@@ -30,7 +30,7 @@ libmysys_a_SOURCES =    my_init.c my_getwd.c mf_getdate.c my_mmap.c \
 			mf_path.c mf_loadpath.c my_file.c \
 			my_open.c my_create.c my_dup.c my_seek.c my_read.c \
 			my_pread.c my_write.c \
-			mf_keycaches.c my_crc32.c \
+			mf_keycache.c mf_keycaches.c my_crc32.c \
 			mf_iocache.c mf_iocache2.c mf_cache.c mf_tempfile.c \
 			mf_tempdir.c my_lock.c mf_brkhant.c my_alarm.c \
 			my_malloc.c my_realloc.c my_once.c mulalloc.c \