Update kdch1 definition to three octal digits.

ncurses wasn't able to detect the delete-character key as KEY_DC.  This
patch fixes that.

kdch1 was defined as "\0177", but terminfo(5) states:
	... characters may be given as three octal digits after a \.

The delete-character key is correctly defined in config.def.h.

st.info

@@ -73,7 +73,7 @@ st| simpleterm,
 	kri=\E[1;2A,
 	kclr=\E[3;5~,
 	kdl1=\E[3;2~,
-	kdch1=\0177,
+	kdch1=\177,
 	kich1=\E[2~,
 	kend=\E[4~,
 	kf1=\EOP,