patch 9.0.1839: No Makefile rule to build cscope database

Problem:  No Makefile rule to build cscope database
Solution: Add rule

Signed-off-by: Christian Brabandt <cb@256bit.org>

src/Makefile

@@ -2151,6 +2151,15 @@ notags:
 tags TAGS: notags
 	$(TAGPRG) $(TAGS_FILES)
 
+# Build the cscope database.
+# This may search more files than necessary.
+.PHONY: cscope csclean
+csclean:
+	-rm -vf cscope.out
+cscope.out:
+	cscope -bv ./*.[ch] ./*.cpp ./if_perl.xs auto/*.h auto/pathdef.c proto/*.pro xxd/xxd.c
+cscope: csclean cscope.out  ;
+
 # Make a highlight file for types.  Requires Exuberant ctags and awk
 types: types.vim
 types.vim: $(TAGS_FILES)

src/version.c

@@ -699,6 +699,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1839,
 /**/
     1838,
 /**/