patch 8.1.1215: "make clean" does not remove generated src/po files

Problem:    "make clean" does not remove generated src/po files.
Solution:   Remove the files for "make clean". (Christian Brabandt)

src/po/Makefile

@@ -151,6 +151,7 @@ prefixcheck:
 
 clean: checkclean
 	rm -f core core.* *.old.po *.mo *.pot sjiscorr
+	rm -f LINGUAS vim.desktop gvim.desktop
 
 distclean: clean
 

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1215,
 /**/
     1214,
 /**/