Disable the Madde plugin by default.

The platform has no vendor support anymore, and the user base is small.

Change-Id: I094482a28502e626077bd1192047d365dcbd5c09
Reviewed-by: hjk <qthjk@ovi.com>

src/plugins/madde/Madde.pluginspec.in

-<plugin name=\"Madde\" version=\"$$QTCREATOR_VERSION\" compatVersion=\"$$QTCREATOR_VERSION\">
+<plugin name=\"Madde\" version=\"$$QTCREATOR_VERSION\" compatVersion=\"$$QTCREATOR_VERSION\" disabledByDefault=\"true\">
     <vendor>Digia Plc</vendor>
     <copyright>(C) 2012 Digia Plc</copyright>
     <license>