Fix file clash in gd tests

Author: nikic

ext/gd/tests/imageloadfont_end_of_file_while_reading_header.phpt

@@ -7,7 +7,7 @@ User Group: PHP-WVL & PHPGent #PHPTestFest
 gd
 --FILE--
 <?php
-$filename = __DIR__ .  '/font.gdf';
+$filename = __DIR__ .  '/imageloadfont_end_of_file_while_reading_header.gdf';
 
 // End of file while reading header
 $bin = "\x41\x41\x41\x41\x00\x00\x00\x00\x00\x00";
@@ -25,7 +25,7 @@ $font = imageloadfont($filename);
 ?>
 --CLEAN--
 <?php
-unlink(__DIR__.'/font.gdf');
+unlink(__DIR__.'/imageloadfont_end_of_file_while_reading_header.gdf');
 ?>
 --EXPECTF--
 Warning: imageloadfont(): End of file while reading header in %s on line %d

ext/gd/tests/imageloadfont_invalid.phpt

@@ -4,7 +4,7 @@ imageloadfont() function crashes
 gd
 --FILE--
 <?php
-$filename = __DIR__ .  '/font.gdf';
+$filename = __DIR__ .  '/imageloadfont_invalid.gdf';
 $bin = "\x41\x41\x41\x41\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x01\x00";
 $fp = fopen($filename, 'wb');
 fwrite($fp, $bin);