Fixed Bug #63435 Datetime::format('u') sometimes wrong by 1 microsecond

When storing '015700' microseconds in a Datetime object,
Datetime::format('u') returns '015699'

Already known per bug45554 reproducer (also fixed).

ext/date/php_date.c

@@ -1095,7 +1095,7 @@ static char *date_format(char *format, int format_len, timelib_time *t, int loca
 			case 'H': length = slprintf(buffer, 32, "%02d", (int) t->h); break;
 			case 'i': length = slprintf(buffer, 32, "%02d", (int) t->i); break;
 			case 's': length = slprintf(buffer, 32, "%02d", (int) t->s); break;
-			case 'u': length = slprintf(buffer, 32, "%06d", (int) floor(t->f * 1000000)); break;
+			case 'u': length = slprintf(buffer, 32, "%06d", (int) floor(t->f * 1000000 + 0.5)); break;
 
 			/* timezone */
 			case 'I': length = slprintf(buffer, 32, "%d", localtime ? offset->is_dst : 0); break;

ext/date/tests/bug45554.phpt

@@ -9,12 +9,12 @@ $d = date_create_from_format($format, "03-15-2005 12:22:29.000000 PST");
 echo $d->format($format), "\n";
 
 $d = date_create_from_format($format, "03-15-2005 12:22:29.001001 PST");
-echo $d->format($format), " (precision isn't enough to show the 1 here)\n";
+echo $d->format($format), "\n";
 
 $d = date_create_from_format($format, "03-15-2005 12:22:29.0010 PST");
 echo $d->format($format), "\n";
 ?>
 --EXPECT--
 03-15-2005 12:22:29.000000 PST
-03-15-2005 12:22:29.001000 PST (precision isn't enough to show the 1 here)
+03-15-2005 12:22:29.001001 PST
 03-15-2005 12:22:29.001000 PST

ext/date/tests/bug63435.phpt

@@ -0,0 +1,16 @@
+--TEST--
+Bug #63435 	Datetime::format('u') sometimes wrong by 1 microsecond
+--INI--
+date.timezone=UTC
+--FILE--
+<?php
+for ($i=1 ; $i<999 ; $i++) {
+	$datetime = Datetime::createFromFormat("u", sprintf("%06ld", $i));
+	$res = $datetime->format("u");
+	if ($res != $i) {
+		echo "$i != $res\n";
+	}
+}
+echo "Done";
+--EXPECT--
+Done