Fix #77700: Writing truecolor images as GIF ignores interlace flag

We  revert the interlace flag related part of commit ff2822a[1], since
contrary to the transparent color, the interlace flag is not retained
by `gdImageCreatePaletteFromTrueColor()`.  This also matches upstream
libgd.

[1] <http://git.php.net/?p=php-src.git;a=commit;h=ff2822a82b740edb8ccf307f080bae188c200fb9>

NEWS

@@ -18,6 +18,10 @@ PHP                                                                        NEWS
   . Fixed bug #50020 (DateInterval:createDateFromString() silently fails).
     (Derick)
 
+- GD:
+  . Fixed bug #77700 (Writing truecolor images as GIF ignores interlace flag).
+    (cmb)
+
 - MySQLi:
   . Fixed bug #77597 (mysqli_fetch_field hangs scripts). (Nikita)
 

ext/gd/libgd/gd_gif_out.c

@@ -132,7 +132,7 @@ void gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)
 	BitsPerPixel = colorstobpp(tim->colorsTotal);
 	/* All set, let's do it. */
 	GIFEncode(
-		out, tim->sx, tim->sy, tim->interlace, 0, tim->transparent, BitsPerPixel,
+		out, tim->sx, tim->sy, interlace, 0, tim->transparent, BitsPerPixel,
 		tim->red, tim->green, tim->blue, tim);
 	if (pim) {
 		/* Destroy palette based temporary image. */

ext/gd/tests/bug77700.phpt

@@ -0,0 +1,24 @@
+--TEST--
+Bug #77700 (Writing truecolor images as GIF ignores interlace flag)
+--SKIPIF--
+<?php
+if (!extension_loaded('gd')) die('skip gd extension not available');
+?>
+--FILE--
+<?php
+$im = imagecreatetruecolor(10, 10);
+imagefilledrectangle($im, 0, 0, 9, 9, imagecolorallocate($im, 255, 255, 255));
+imageinterlace($im, 1);
+imagegif($im, __DIR__ . 'bug77700.gif');
+
+$im = imagecreatefromgif(__DIR__ . 'bug77700.gif');
+var_dump(imageinterlace($im));
+?>
+===DONE===
+--EXPECT--
+int(1)
+===DONE===
+--CLEAN--
+<?php
+unlink(__DIR__ . 'bug77700.gif');
+?>