Fix #66882: imagerotate by -90 degrees truncates image by 1px

Contrary to the external libgd, the bundled libgd doesn't use optimized
rotation algorithms for negative square angles. We fix that now.

There are other improvements in gdImageRotateInterpolated() in the external
libgd. I'll leave them out for now, in the hope that we'll be able to rejoin
the two libraries rather soon.

ext/gd/libgd/gd_interpolation.c

@@ -2178,10 +2178,13 @@ gdImagePtr gdImageRotateInterpolated(const gdImagePtr src, const float angle, in
 
 	/* no interpolation needed here */
 	switch (angle_rounded) {
-		case 9000:
+		case -27000:
+		case   9000:
 			return gdImageRotate90(src, 0);
-		case 18000:
+		case -18000:
+		case  18000:
 			return gdImageRotate180(src, 0);
+		case -9000:
 		case 27000:
 			return gdImageRotate270(src, 0);
 	}

ext/gd/tests/bug66882.phpt

@@ -0,0 +1,14 @@
+--TEST--
+Bug #66882 (imagerotate by -90 degrees truncates image by 1px)
+--SKIPIF--
+<?php
+if (!extension_loaded('gd')) die('skip gd extension not available');
+?>
+--FILE--
+<?php
+$im = imagerotate(imagecreate(10, 10), -90, 0);
+var_dump(imagesy($im), imagesx($im));
+?>
+--EXPECT--
+int(10)
+int(10)