Reentrant versions of localtime and gmtime.

[Joel Tornatore]

##  From eggert at twinsun.com Mon Oct 30 20:06:39 1995
##  
##     Date: Mon, 30 Oct 1995 17:13:53 -0800
##     From: "J.T. Conklin" <jtc at cygnus.com>
##  
##       struct tm *
##     + localtime_r(timep, res)
##     + const time_t * const    timep;
##     + struct tm *             tm;
##     + {
##     + 	tzset();
##     + 	localsub(timep, 0L, tm);
##     + 	return tm;
##     + }
##  
##  That isn't reentrant, since tzset() isn't reentrant.


Solaris solves this problem with a mutex lock that is
acquired by all functions, including the _r versions.

joel