x11-toolkits/scintilla: prepare for glib-2.68.3

Add upstream fix removing 'volatile'

Obtained from:	https://sourceforge.net/p/scintilla/code/ci/790bfd4c0747
PR:		256200

x11-toolkits/scintilla/files/patch-hg_8719-790bfd4c0747_fix-glib_2.68.3

@@ -0,0 +1,33 @@
+# HG changeset patch
+# User Neil Hodgson <nyamatongwe@gmail.com>
+# Date 1619159850 -36000
+#      Fri Apr 23 16:37:30 2021 +1000
+# Node ID 790bfd4c0747eb5e0bc4d627a101298207a8421e
+# Parent  bf180d712ff771fe40a2d5dc178fa0a15cf14b2d
+Remove volatile qualifiers as they cause an error with Clang 12.
+The glib documentation shows use without volatile and mentions that -
+    While location has a volatile qualifier, this is a historical artifact and
+    the pointer passed to it should not be volatile.
+https://developer.gnome.org/glib/stable/glib-Threads.html#g-once-init-enter
+
+diff -r bf180d712ff7 -r 790bfd4c0747 gtk/ScintillaGTKAccessible.cxx
+--- gtk/ScintillaGTKAccessible.cxx	Fri Apr 23 16:05:55 2021 +1000
++++ gtk/ScintillaGTKAccessible.cxx	Fri Apr 23 16:37:30 2021 +1000
+@@ -1008,7 +1008,7 @@
+
+ // @p parent_type is only required on GTK 3.2 to 3.6, and only on the first call
+ static GType scintilla_object_accessible_get_type(GType parent_type G_GNUC_UNUSED) {
+-	static volatile gsize type_id_result = 0;
++	static gsize type_id_result = 0;
+
+ 	if (g_once_init_enter(&type_id_result)) {
+ 		GTypeInfo tinfo = {
+@@ -1099,7 +1099,7 @@
+ #if HAVE_GTK_A11Y_H // just instantiate the accessible
+ 	*cache = scintilla_object_accessible_new(0, G_OBJECT(widget));
+ #elif HAVE_GTK_FACTORY // register in the factory and let GTK instantiate
+-	static volatile gsize registered = 0;
++	static gsize registered = 0;
+
+ 	if (g_once_init_enter(&registered)) {
+ 		// Figure out whether accessibility is enabled by looking at the type of the accessible