visualgst: Remove debugger extensions in favor of using DebugTools

Do not have Debugger extensions in VisualGST. The DebugTools
package should provide everything that is necessary to create
a working debugger. Remove the extensions and rely on the
DebugTools.

2013-06-18  Gwenael Casaccio  <gwenael.casaccio@gmail.com>

	* Debugger/GtkDebugger.st: Don't use previous debugger extensions.
	* Extensions.st: Remove the debugger extension.