Added PSR-4 compatible autoloader as defined at http://www.php-fig.org/psr/psr-4/.

SurfaceActiveCall.php was split into four files. Each file must contain exactly one PHP class because of the following line in the spec:

> The terminating class name corresponds to a file name ending in .php. The file name MUST match the case of the terminating class name.

Other changes were made to correctly import the library using the autoloader.
	Change on 2015/01/02 by mlumish <mlumish@google.com>
-------------
Created by MOE: http://code.google.com/p/moe-java
MOE_MIGRATED_REVID=83150065
diff --git a/src/php/tests/interop/interop_client.php b/src/php/tests/interop/interop_client.php
index 9810c86..43da47f 100755
--- a/src/php/tests/interop/interop_client.php
+++ b/src/php/tests/interop/interop_client.php
@@ -1,7 +1,5 @@
 <?php
-require __DIR__ . '/../../lib/Grpc/ActiveCall.php';
-require __DIR__ . '/../../lib/Grpc/SurfaceActiveCall.php';
-require __DIR__ . '/../../lib/Grpc/BaseStub.php';
+require_once realpath(dirname(__FILE__) . '/../../lib/autoload.php');
 require 'DrSlump/Protobuf.php';
 \DrSlump\Protobuf::autoload();
 require 'empty.php';