Make (STATUS DATE) return a four-digit year.

This is a change to the API, but existing users are already inconsistent
in how they handle 2-digit years -- some assume it's year % 100 (as the
documentation says), some assume it's year - 1900, and some
string-prepend "19" -- so most have Y2K problems that need fixing.

As it's now reading the date using two UUOs, it needs to be careful to
check that the year hasn't rolled over between the two, as LIBDOC; TIME
does for the day.

I've updated all four implementations of SDATE, but only tested the ITS
version.

src/l/status.266

@@ -617,15 +617,26 @@ SUBTTL	STATUS TIME, DATE, UNAME, USERID, JNAME, JNUMBER, SUBSYSTEM
 IFN ITS,[
 
 STIME:	.RTIME TT,
-	JRST SDATE+1
-
-SDATE:	.RDATE TT,
 	AOJE TT,FALSE
 	MOVE D,TT
 	SUB D,[202020202021]	;21 ADJUSTS FOR THE AOJE
-	JSP F,STCVT
-	JSP F,STCVT
-	JSP F,STCVT
+	JSP F,STCVT		;Hour
+	JRST SDAT2
+
+SDATE:	.RYEAR T,		;Get year info
+	JUMPE T,FALSE
+	.RDATE D,		;Get sixbit date
+	AOJE D,FALSE
+	.RYEAR TT,		;Has the year just rolled over?
+	CAME T,TT
+	 JRST SDATE		; Happy new year! Try again
+	HRRZ TT,T		;4-digit year
+	JSP T,FXCONS
+	PUSH P,A
+	SUB D,[202020202021]	;21 adjusts for the AOJE
+	LSH D,12.		;Discard 2-digit year
+SDAT2:	JSP F,STCVT		;Month  (or minute)
+	JSP F,STCVT		;Day    (or second)
 	MOVNI T,3
 	JRST LIST
 
@@ -710,7 +721,6 @@ SDATE:	MOVE R,[%CNYER]
 	MOVE TT,[%CNDAY]
 	GETTAB R,
 	 JRST FALSE
-	SUBI R,1900.
 	JRST STIM2
 
 STIME:	MOVE R,[%CNHOR]
@@ -741,7 +751,7 @@ SDATE:	DATE D,			;DATE IN D = <<YEAR-1964.>*12.+MONTH-1>*31.+DAY-1
 	MOVE T,R
 	IDIVI D,12.		;REMAINDER HERE IS MONTH-1
 	AOJ R,
-	ADDI D,64.		;QUOTIENT IN D IS YEAR-1964.
+	ADDI D,1964.		;QUOTIENT IN D IS YEAR-1964.
 	PUSH FXP,D
 	PUSH FXP,R
 	PUSH FXP,T
@@ -812,7 +822,6 @@ STIME1:	PUSHJ P,CONS1FX		;CONS R, D, TT INTO A LIST OF FIXNUMS
 SDATE:	PUSHJ P,SDATIM		;RETURNS DATE IN D AND R
 	HLRZ TT,R		;DAY-1
 	HLRZ R,D		;YEAR
-	SUBI R,1900.		;REDUCE IT TO A YEAR MOD 100.
 	MOVEI D,1(D)		;MONTH
 	AOJA TT,STIME1		;INCREMENT DAY-1 TO DAY, AND GO CONS