Parse primary device attributes as well as secondary and add a SIXEL

flag (not used yet), from Anindya Mukherjee.

tmux.h

@@ -543,6 +543,7 @@ enum tty_code_code {
 	TTYC_SMUL,
 	TTYC_SMULX,
 	TTYC_SMXX,
+	TTYC_SXL,
 	TTYC_SS,
 	TTYC_SWD,
 	TTYC_SYNC,
@@ -1349,6 +1350,7 @@ struct tty_term {
 #define TERM_DECFRA 0x8
 #define TERM_RGBCOLOURS 0x10
 #define TERM_VT100LIKE 0x20
+#define TERM_SIXEL 0x40
 	int		 flags;
 
 	LIST_ENTRY(tty_term) entry;
@@ -1405,9 +1407,10 @@ struct tty {
 #define TTY_OPENED 0x20
 #define TTY_OSC52QUERY 0x40
 #define TTY_BLOCK 0x80
-#define TTY_HAVEDA 0x100
+#define TTY_HAVEDA 0x100 /* Primary DA. */
 #define TTY_HAVEXDA 0x200
 #define TTY_SYNCING 0x400
+#define TTY_HAVEDA2 0x800 /* Seconday DA. */
 	int		 flags;
 
 	struct tty_term	*term;