patch 8.0.1773: dialog messages are not translated

Problem:    Dialog messages are not translated.
Solution:   Add N_() and _() where needed. (Sergey Alyoshin)
diff --git a/src/diff.c b/src/diff.c
index b69b69e..cc9e6de 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -909,7 +909,8 @@
     if (cmdmod.browse)
     {
 	browseFile = do_browse(0, (char_u *)_("Patch file"),
-			 eap->arg, NULL, NULL, BROWSE_FILTER_ALL_FILES, NULL);
+			 eap->arg, NULL, NULL,
+			 (char_u *)_(BROWSE_FILTER_ALL_FILES), NULL);
 	if (browseFile == NULL)
 	    return;		/* operation cancelled */
 	eap->arg = browseFile;