Make zlib include_path tests more robust

One file is placed inside the script directory, we need to make
sure it has a unique name as well.

Author: nikic

ext/zlib/tests/gzfile_variation15.phpt

@@ -8,7 +8,7 @@ if (!extension_loaded("zlib")) {
 ?>
 --FILE--
 <?php
-$thisTestDir = 'gzfile_variation15.dir';
+$testName = 'gzfile_variation15';
 require_once('reading_include_path.inc');
 
 //define the files to go into these directories, create one in dir2

ext/zlib/tests/gzopen_variation4.phpt

@@ -16,7 +16,7 @@ if (!extension_loaded("zlib")) {
 
 echo "*** Testing gzopen() : usage variation ***\n";
 
-$thisTestDir = 'gzopen_variation4.dir';
+$testName = 'gzopen_variation4';
 require_once('reading_include_path.inc');
 
 //define the files to go into these directories, create one in dir2

ext/zlib/tests/readgzfile_variation15.phpt

@@ -8,7 +8,7 @@ if (!extension_loaded("zlib")) {
 ?>
 --FILE--
 <?php
-$thisTestDir = 'readgzfile_variation15.dir';
+$testName = 'readgzfile_variation15';
 require_once('reading_include_path.inc');
 
 //define the files to go into these directories, create one in dir2

ext/zlib/tests/reading_include_path.inc

@@ -1,10 +1,11 @@
 <?php
+$thisTestDir = $testName . '.dir';
 mkdir($thisTestDir);
 chdir($thisTestDir);
 
 //create the include directory structure
 $workingDir = "workdir";
-$filename = "afile.txt.gz";
+$filename = $testName . ".txt.gz";
 $scriptDir = dirname(__FILE__);
 $baseDir = getcwd();
 $secondFile = $baseDir."/dir2/".$filename;