Remove initialization of static or global values to zero, throughout. This

just needlessly grows the size of the DLL.
* tty.cc (tty::alive): Make inuse handle non-inheriting on open, just for
thread safety.

winsup/cygwin/localtime.cc

@@ -640,12 +640,12 @@ static struct tm	tm;
 #undef _daylight
 
 #ifdef USG_COMPAT
-time_t			timezone = 0;
-int			daylight = 0;
+time_t			timezone;
+int			daylight;
 #endif /* defined USG_COMPAT */
 
 #ifdef ALTZONE
-time_t			altzone = 0;
+time_t			altzone;
 #endif /* defined ALTZONE */
 
 static long