If the terminal supports sitm for italics, use it instead of standout

(smso). From Tiago Resende.

tty-term.c

@@ -178,6 +178,7 @@ const struct tty_term_code_entry tty_term_codes[NTTYCODE] = {
 	{ TTYC_SMKX, TTYCODE_STRING, "smkx" },
 	{ TTYC_SMSO, TTYCODE_STRING, "smso" },
 	{ TTYC_SMUL, TTYCODE_STRING, "smul" },
+	{ TTYC_SITM, TTYCODE_STRING, "sitm" },
 	{ TTYC_VPA, TTYCODE_STRING, "vpa" },
 	{ TTYC_XENL, TTYCODE_FLAG, "xenl" },
 };