Added Support for QString slots

[Marcus <ma...@my...>]

Today I added support for slots that accept a signal QString parameter. Using 
this type of slot has a couple of tricks because of the way strings are 
mapped in this version of Qt#: in the places where the C++ member function 
takes a QString, the C# equivalent uses a string. (The Qt# binding takes care 
of the conversion.) Qt#'s signal connection code expected to find a slot with 
the same parameter type(s) as the signal.

Suppose that I want to connect a QLineEdit's textchanged signal to a QLabel's 
setText slot. The QLineEdit actually has a parameter with type QString, but 
QLabel's SetText takes a *string* parameter. As a consequence, you can only 
connect to a user-defined slot like

	public void StringSlot(QString s)

For an example, see the attached file qstring-slot.cs, also found  in the 
samples directory in CVS (QTSHARP-0_6_BRANCH).