patch 8.1.0528: various typos in comments

Problem:    Various typos in comments.
Solution:   Fix the typos.
diff --git a/src/gui.c b/src/gui.c
index 1341d50..6154b48 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -5501,7 +5501,7 @@
 	    p = NULL;
 
 	/* Handle the drop, :edit or :split to get to the file.  This also
-	 * frees fnames[].  Skip this if there is only one item it's a
+	 * frees fnames[].  Skip this if there is only one item, it's a
 	 * directory and Shift is held down. */
 	if (count == 1 && (modifiers & MOUSE_SHIFT) != 0
 						     && mch_isdir(fnames[0]))