Description:
------------
If I create a truecolor image and
a) set a color as transparent
b) use imagetruecolortopalette
the result is offset by one in "x" direction and a black vertical line at x=0.

Leaving out either a or b gives the correct result (no offset).

Didn't find this bug anywhere, am however unable to compile on Windows.

Reproduce code:
---------------
<?php
		header( "Content-Type: image/png" );

		$im = imagecreatetruecolor( 750, 400 );

		$bg = imagecolorallocate( $im, 0xFF, 0xAA, 0xAA );
		imagecolortransparent( $im, $bg );											// EITHER THIS
		imagefilledrectangle( $im, 0, 0, 749, 399, $bg );

		$c2 = imagecolorallocate( $im, 0x01, 0x23, 0x45 );
		imagerectangle( $im, 0, 0, 749, 399, $c2 );

		imagetruecolortopalette( $im, false, 256 );							// OR THAT
		imagepng( $im );
?>

Expected result:
----------------
palette image, 750x400 with a rectangle along the borders

Actual result:
--------------
palette image, 750x400, with a rectangle open to the right (offset 1)