intl: Fork get_cp_config_name off get_cp_mime_name.

This may help with bug 914 but I'm not testing that yet.

src/config/opttypes.c

@@ -322,7 +322,7 @@ cp_set(struct option *opt, unsigned char *str)
 static void
 cp_wr(struct option *o, struct string *s)
 {
-	unsigned char *mime_name = get_cp_mime_name(o->value.number);
+	unsigned char *mime_name = get_cp_config_name(o->value.number);
 
 	add_optstring_to_string(s, mime_name, strlen(mime_name));
 }

src/dialogs/options.c

@@ -64,7 +64,7 @@ charset_list(struct terminal *term, void *xxx, void *ses_)
 
 		items++;
 		add_to_menu(&mi, name, NULL, ACT_MAIN_NONE,
-			    display_codepage, get_cp_mime_name(i), 0);
+			    display_codepage, get_cp_config_name(i), 0);
 	}
 
 	/* Special codepages are not in the menu and it may cause assertion

src/intl/charsets.c

@@ -1427,6 +1427,11 @@ free_charsets_lookup(void)
 #endif
 }
 
+/* Get the codepage's name for displaying to the user, or NULL if
+ * @cp_index is one past the end.  In the future, we might want to
+ * localize these with gettext.  So it may be best not to use this
+ * function if the name will have to be converted back to an
+ * index.  */
 unsigned char *
 get_cp_name(int cp_index)
 {
@@ -1436,11 +1441,27 @@ get_cp_name(int cp_index)
 	return codepages[cp_index].name;
 }
 
+/* Get the codepage's name for saving to a configuration file.  These
+ * names can be converted back to indexes, even in future versions of
+ * ELinks.  */
+unsigned char *
+get_cp_config_name(int cp_index)
+{
+	if (cp_index < 0) return "none";
+	if (cp_index & SYSTEM_CHARSET_FLAG) return "System";
+	if (!codepages[cp_index].aliases) return NULL;
+
+	return codepages[cp_index].aliases[0];
+}
+
+/* Get the codepage's name for sending to a library or server that
+ * understands MIME charset names.  This function irreversibly maps
+ * the "System" codepage to the underlying charset.  */
 unsigned char *
 get_cp_mime_name(int cp_index)
 {
 	if (cp_index < 0) return "none";
-	if (cp_index & SYSTEM_CHARSET_FLAG) return "System";
+	cp_index &= ~SYSTEM_CHARSET_FLAG;
 	if (!codepages[cp_index].aliases) return NULL;
 
 	return codepages[cp_index].aliases[0];

src/intl/charsets.h

@@ -106,6 +106,7 @@ unsigned char *convert_string(struct conv_table *convert_table,
 
 int get_cp_index(unsigned char *);
 unsigned char *get_cp_name(int);
+unsigned char *get_cp_config_name(int);
 unsigned char *get_cp_mime_name(int);
 int is_cp_utf8(int);
 void free_conv_table(void);

src/scripting/lua/core.c

@@ -579,7 +579,7 @@ l_get_option(LS)
 	{
 		unsigned char *cp_name;
 
-		cp_name = get_cp_mime_name(opt->value.number);
+		cp_name = get_cp_config_name(opt->value.number);
 		lua_pushstring(S, cp_name);
 		break;
 	}