Fix default minimum value for descending sequences

For some reason that is lost in history, a descending sequence would
default its minimum value to -2^63+1 (-PG_INT64_MAX) instead of
-2^63 (PG_INT64_MIN), even though explicitly specifying a minimum value
of -2^63 would work.  Fix this inconsistency by using the full range by
default.
Reported-by: Daniel Verite <daniel@manitou-mail.org>
Reviewed-by: Michael Paquier <michael.paquier@gmail.com>

doc/src/sgml/ref/create_sequence.sgml

@@ -133,7 +133,7 @@ SELECT * FROM <replaceable>name</replaceable>;
       the minimum value a sequence can generate. If this clause is not
       supplied or <option>NO MINVALUE</option> is specified, then
       defaults will be used.  The defaults are 1 and
-      -2<superscript>63</>-1 for ascending and descending sequences,
+      -2<superscript>63</> for ascending and descending sequences,
       respectively.
      </para>
     </listitem>

src/backend/commands/sequence.c

@@ -1353,7 +1353,7 @@ init_params(ParseState *pstate, List *options, bool isInit,
 	else if (isInit || max_value != NULL)
 	{
 		if (seqform->seqincrement > 0)
-			seqform->seqmax = SEQ_MAXVALUE;		/* ascending seq */
+			seqform->seqmax = PG_INT64_MAX;		/* ascending seq */
 		else
 			seqform->seqmax = -1;	/* descending seq */
 		seqdataform->log_cnt = 0;
@@ -1370,7 +1370,7 @@ init_params(ParseState *pstate, List *options, bool isInit,
 		if (seqform->seqincrement > 0)
 			seqform->seqmin = 1; /* ascending seq */
 		else
-			seqform->seqmin = SEQ_MINVALUE;		/* descending seq */
+			seqform->seqmin = PG_INT64_MIN;		/* descending seq */
 		seqdataform->log_cnt = 0;
 	}
 

src/bin/pg_dump/pg_dump.c

@@ -15876,8 +15876,8 @@ dumpSequence(Archive *fout, TableInfo *tbinfo)
 	/* Make sure we are in proper schema */
 	selectSourceSchema(fout, tbinfo->dobj.namespace->dobj.name);
 
-	snprintf(bufm, sizeof(bufm), INT64_FORMAT, SEQ_MINVALUE);
-	snprintf(bufx, sizeof(bufx), INT64_FORMAT, SEQ_MAXVALUE);
+	snprintf(bufm, sizeof(bufm), INT64_FORMAT, PG_INT64_MIN);
+	snprintf(bufx, sizeof(bufx), INT64_FORMAT, PG_INT64_MAX);
 
 	if (fout->remoteVersion >= 100000)
 	{

src/include/pg_config_manual.h

@@ -50,12 +50,6 @@
  */
 #define PARTITION_MAX_KEYS	32
 
-/*
- * Set the upper and lower bounds of sequence values.
- */
-#define SEQ_MAXVALUE	PG_INT64_MAX
-#define SEQ_MINVALUE	(-SEQ_MAXVALUE)
-
 /*
  * When we don't have native spinlocks, we use semaphores to simulate them.
  * Decreasing this value reduces consumption of OS resources; increasing it