Update timezone code to track the upstream changes since 2003. In particular

this adds support for 64-bit tzdata files, which is needed to support DST
calculations beyond 2038.  Add a regression test case to give some minimal
confidence that that really works.

Heikki Linnakangas

src/timezone/tzfile.h

@@ -3,10 +3,10 @@
 
 /*
  * This file is in the public domain, so clarified as of
- * 1996-06-05 by Arthur David Olson (arthur_david_olson@nih.gov).
+ * 1996-06-05 by Arthur David Olson.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/timezone/tzfile.h,v 1.6 2005/10/15 02:49:51 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/timezone/tzfile.h,v 1.7 2008/02/16 21:16:04 tgl Exp $
  */
 
 /*
@@ -33,7 +33,8 @@
 struct tzhead
 {
 	char		tzh_magic[4];	/* TZ_MAGIC */
-	char		tzh_reserved[16];		/* reserved for future use */
+	char		tzh_version[1]; /* '\0' or '2' as of 2005 */
+	char		tzh_reserved[15];		/* reserved--must be zero */
 	char		tzh_ttisgmtcnt[4];		/* coded number of trans. time flags */
 	char		tzh_ttisstdcnt[4];		/* coded number of trans. time flags */
 	char		tzh_leapcnt[4]; /* coded number of leap seconds */
@@ -68,18 +69,22 @@ struct tzhead
  *----------
  */
 
+/*
+ * If tzh_version is '2' or greater, the above is followed by a second instance
+ * of tzhead and a second instance of the data in which each coded transition
+ * time uses 8 rather than 4 chars,
+ * then a POSIX-TZ-environment-variable-style string for use in handling
+ * instants after the last transition time stored in the file
+ * (with nothing between the newlines if there is no POSIX representation for
+ * such instants).
+ */
+
 /*
  * In the current implementation, "tzset()" refuses to deal with files that
  * exceed any of the limits below.
  */
 
-/*
- * The TZ_MAX_TIMES value below is enough to handle a bit more than a
- * year's worth of solar time (corrected daily to the nearest second) or
- * 138 years of Pacific Presidential Election time
- * (where there are three time zone transitions every fourth year).
- */
-#define TZ_MAX_TIMES	370
+#define TZ_MAX_TIMES	1200
 
 #define TZ_MAX_TYPES	256		/* Limited by what (unsigned char)'s can hold */
 
@@ -124,11 +129,20 @@ struct tzhead
 #define EPOCH_YEAR	1970
 #define EPOCH_WDAY	TM_THURSDAY
 
-/*
- * Accurate only for the past couple of centuries;
- * that will probably do.
- */
-
 #define isleap(y) (((y) % 4) == 0 && (((y) % 100) != 0 || ((y) % 400) == 0))
 
+/*
+ * Since everything in isleap is modulo 400 (or a factor of 400), we know that
+ *    isleap(y) == isleap(y % 400)
+ * and so
+ *    isleap(a + b) == isleap((a + b) % 400)
+ * or
+ *    isleap(a + b) == isleap(a % 400 + b % 400)
+ * This is true even if % means modulo rather than Fortran remainder
+ * (which is allowed by C89 but not C99).
+ * We use this to avoid addition overflow problems.
+ */
+
+#define isleap_sum(a, b)      isleap((a) % 400 + (b) % 400)
+
 #endif   /* !defined TZFILE_H */