Make GUC_check_errdetail messages full sentences

They were all missing punctuation, one was missing initial capital.
Per our message style guidelines.

No backpatch, to avoid breaking existing translations.

src/backend/access/transam/slru.c

@@ -358,7 +358,7 @@ check_slru_buffers(const char *name, int *newval)
 	if (*newval % SLRU_BANK_SIZE == 0)
 		return true;
 
-	GUC_check_errdetail("\"%s\" must be a multiple of %d", name,
+	GUC_check_errdetail("\"%s\" must be a multiple of %d.", name,
 						SLRU_BANK_SIZE);
 	return false;
 }

src/backend/access/transam/xlogrecovery.c

@@ -4933,7 +4933,7 @@ check_recovery_target_time(char **newval, void **extra, GucSource source)
 
 			if (tm2timestamp(tm, fsec, &tz, &timestamp) != 0)
 			{
-				GUC_check_errdetail("timestamp out of range: \"%s\"", str);
+				GUC_check_errdetail("Timestamp out of range: \"%s\".", str);
 				return false;
 			}
 		}

src/backend/commands/vacuum.c

@@ -130,7 +130,8 @@ check_vacuum_buffer_usage_limit(int *newval, void **extra,
 		return true;
 
 	/* Value does not fall within any allowable range */
-	GUC_check_errdetail("\"vacuum_buffer_usage_limit\" must be 0 or between %d kB and %d kB",
+	GUC_check_errdetail("\"%s\" must be 0 or between %d kB and %d kB.",
+						"vacuum_buffer_usage_limit",
 						MIN_BAS_VAC_RING_SIZE_KB, MAX_BAS_VAC_RING_SIZE_KB);
 
 	return false;

src/backend/replication/slot.c

@@ -2478,7 +2478,7 @@ validate_sync_standby_slots(char *rawname, List **elemlist)
 
 			if (!slot)
 			{
-				GUC_check_errdetail("replication slot \"%s\" does not exist",
+				GUC_check_errdetail("Replication slot \"%s\" does not exist.",
 									name);
 				ok = false;
 				break;
@@ -2486,7 +2486,7 @@ validate_sync_standby_slots(char *rawname, List **elemlist)
 
 			if (!SlotIsPhysical(slot))
 			{
-				GUC_check_errdetail("\"%s\" is not a physical replication slot",
+				GUC_check_errdetail("\"%s\" is not a physical replication slot.",
 									name);
 				ok = false;
 				break;

src/backend/replication/syncrep.c

@@ -1010,7 +1010,8 @@ check_synchronous_standby_names(char **newval, void **extra, GucSource source)
 			if (syncrep_parse_error_msg)
 				GUC_check_errdetail("%s", syncrep_parse_error_msg);
 			else
-				GUC_check_errdetail("\"synchronous_standby_names\" parser failed");
+				GUC_check_errdetail("\"%s\" parser failed.",
+									"synchronous_standby_names");
 			return false;
 		}
 

src/backend/storage/file/fd.c

@@ -3985,7 +3985,7 @@ check_debug_io_direct(char **newval, void **extra, GucSource source)
 
 	if (!SplitGUCList(rawstring, ',', &elemlist))
 	{
-		GUC_check_errdetail("Invalid list syntax in parameter \"%s\"",
+		GUC_check_errdetail("Invalid list syntax in parameter \"%s\".",
 							"debug_io_direct");
 		pfree(rawstring);
 		list_free(elemlist);
@@ -4005,7 +4005,7 @@ check_debug_io_direct(char **newval, void **extra, GucSource source)
 			flags |= IO_DIRECT_WAL_INIT;
 		else
 		{
-			GUC_check_errdetail("Invalid option \"%s\"", item);
+			GUC_check_errdetail("Invalid option \"%s\".", item);
 			result = false;
 			break;
 		}
@@ -4018,7 +4018,7 @@ check_debug_io_direct(char **newval, void **extra, GucSource source)
 #if XLOG_BLCKSZ < PG_IO_ALIGN_SIZE
 	if (result && (flags & (IO_DIRECT_WAL | IO_DIRECT_WAL_INIT)))
 	{
-		GUC_check_errdetail("\"%s\" is not supported for WAL because %s is too small",
+		GUC_check_errdetail("\"%s\" is not supported for WAL because %s is too small.",
 							"debug_io_direct", "XLOG_BLCKSZ");
 		result = false;
 	}
@@ -4026,7 +4026,7 @@ check_debug_io_direct(char **newval, void **extra, GucSource source)
 #if BLCKSZ < PG_IO_ALIGN_SIZE
 	if (result && (flags & IO_DIRECT_DATA))
 	{
-		GUC_check_errdetail("\"%s\" is not supported for WAL because %s is too small",
+		GUC_check_errdetail("\"%s\" is not supported for WAL because %s is too small.",
 							"debug_io_direct", "BLCKSZ");
 		result = false;
 	}

src/backend/utils/error/elog.c

@@ -2183,7 +2183,7 @@ check_backtrace_functions(char **newval, void **extra, GucSource source)
 					  ", \n\t");
 	if (validlen != newvallen)
 	{
-		GUC_check_errdetail("Invalid character");
+		GUC_check_errdetail("Invalid character.");
 		return false;
 	}