patch 8.2.0464: typos and other small problems

Problem:    Typos and other small problems.
Solution:   Fix the typos.  Add missing files to the distribution.
diff --git a/src/gui_gtk_x11.c b/src/gui_gtk_x11.c
index ef930a5..ea43c93 100644
--- a/src/gui_gtk_x11.c
+++ b/src/gui_gtk_x11.c
@@ -4743,6 +4743,8 @@
 	PangoCoverage	*coverage;
 	gunichar	uc;
 
+	// Valgrind reports a leak for pango_language_from_string(), but the
+	// documentation says "This is owned by Pango and should not be freed".
 	coverage = pango_font_get_coverage(
 		font, pango_language_from_string(cjk_langs[i]));