moved term.hidec in term.c for consistency, put back delay in xbell()

along with duration in config.h, factored some code in tnew()/treset()
and cleaned some code.

config.h

@@ -30,6 +30,7 @@ static const char *colorname[] = {
 #define DefaultBG 0
 #define DefaultCS 1
 #define BellCol   DefaultFG
+#define BellTime  30000 /* microseconds */
 
 /* special keys */
 static Key key[] = {