Only allow NuSOAP to compress SOAP responses

When NuSOAP receives a request which declares that it accepts a compressed (gzip,deflate)
response, it performs its own compression. Although conceptually incorrect, since this
should be handled by the web server, there is no configuration flag to disable it.

Therefore we disable all forms of compression for the SOAP API and allow NuSOAP to perform
the compression itself.

Fixes #11868: returned compressed data corrupt

api/soap/mantisconnect.php

@@ -6,6 +6,12 @@
 # change the license of future releases.
 # See docs/ folder for more details
 
+// NuSOAP already performs compression,
+// so we prevent a double-compression.
+// See issue #11868 for details
+define( 'COMPRESSION_DISABLED', true);
+ini_set( 'zlib.output_compression', false );
+
 set_include_path( '../../library' );
 require_once( 'nusoap/nusoap.php' );