Fix two more problems with time zones and epoch handling

src/cmd/ksh93/edit/history.c:
 - The `time_t` data type is usually 64-bit, so cast `t` to an
   unsigned long and use the correct format specifier with sfprintf.

src/lib/libast/tm/tmdata.c:
 - Update the leap second array by adding the current leap
   seconds that were absent, being:

   2016-12-31+23:59:60  1483228826
   2015-06-30+23:59:60  1435708825
   2012-06-30+23:59:60  1341100824

   I couldn't find a proper list of leap seconds in Unix Epoch time,
   so I used an Epoch Converter:
   https://www.epochconverter.com/
   The converter doesn't support leap seconds, so each conversion
   had to be corrected by adding the number of leap seconds required
   (e.g. 1230767999 + 24 = 1230768023, for 2008-12-31+23:59:60 in GMT).

src/cmd/ksh93/edit/history.c

@@ -834,7 +834,7 @@ static int hist_write(Sfio_t *iop,const void *buff,register int insize,Sfdisc_t*
 	if(hp->auditfp)
 	{
 		time_t	t=time((time_t*)0);
-		sfprintf(hp->auditfp,"%u;%u;%s;%*s%c",sh_isoption(SH_PRIVILEGED)?shgd->euserid:shgd->userid,t,hp->tty,size,buff,0);
+		sfprintf(hp->auditfp,"%u;%lu;%s;%*s%c",sh_isoption(SH_PRIVILEGED)?shgd->euserid:shgd->userid,(unsigned long)t,hp->tty,size,buff,0);
 		sfsync(hp->auditfp);
 	}
 #endif	/* SHOPT_AUDIT */

src/lib/libast/tm/tmdata.c

@@ -189,6 +189,9 @@ static short	sum[] = { 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 36
 
 static Tm_leap_t	leap[] =
 {
+	 1483228826,   27,		/* 2016-12-31+23:59:60-0000 */
+	 1435708825,   26,		/* 2015-06-30+23:59:60-0000 */
+	 1341100824,   25,		/* 2012-06-30+23:59:60-0000 */
 	 1230768023,   24,		/* 2008-12-31+23:59:60-0000 */
 	 1136073622,   23,		/* 2005-12-31+23:59:60-0000 */
 	  915148821,   22,		/* 1998-12-31+23:59:60-0000 */