* src/input/input.c: honor the --demux config option (will be overriden if demux is specified in the MRL).
   I'm not exactly sure this is wise as some users will surely fuck-up their preferences and force a specific demux...
   but this also allows me to specifiy the demuxdump demux with an input option (very handy to include the demuxdump option in the streamout gui dialogs).
* src/misc/modules.c: changed module_Need() to use var_Get() instead of config_Get.

* modules/gui/wxwindows/*: moved the demuxdump option from the open dialog to the streamout dialog.