xim: one file at the top level, keymaplookup in it

xim/keymap.c held one 37-line function apart from xim.c, with its own
prototype typed by hand in xim.c and nelem spelt out because it avoided
dat.h — all so that a test could link it without imdkit, though the XIM
adapter test #includes xim.c whole anyway.  It lives in xim.c now, and
xim.c, the last file of its directory, sits beside ibus.c.

Makefile

@@ -20,10 +20,8 @@ DOCKER_RUN = docker run --rm --user "$$(id -u):$$(id -g)" \
 	-v "$(CURDIR):/src" $(DOCKER_IMAGE)
 
 SRCS = dict.c font.c ibus.c ipc.c ko.c main.c popup_layout.c \
-	srv.c str.c strans.c trie.c vi.c win.c
-XIMSRCS = xim/xim.c xim/keymap.c
-XIMOBJS = $(XIMSRCS:.c=.o)
-OBJS = $(SRCS:.c=.o) $(XIMOBJS)
+	srv.c str.c strans.c trie.c vi.c win.c xim.c
+OBJS = $(SRCS:.c=.o)
 
 all: $(PROG) gtk
 
@@ -34,7 +32,7 @@ $(OBJS): dat.h fn.h ipc.h
 ibus.o: PROJECT_CPPFLAGS += $(IBUS_CFLAGS)
 font.o: PROJECT_CPPFLAGS += $(TEXT_CFLAGS)
 win.o: PROJECT_CPPFLAGS += $(POPUP_CFLAGS)
-$(XIMOBJS): PROJECT_CPPFLAGS += -I. $(XIM_CFLAGS)
+xim.o: PROJECT_CPPFLAGS += $(XIM_CFLAGS)
 
 %.o: %.c
 	$(CC) $(CPPFLAGS) $(PROJECT_CPPFLAGS) $(WARN_CFLAGS) $(CFLAGS) -c -o $@ $<