[Merkaartor] Qt4.4 needed for compilation

[Martin Dobias]

Hi,

I've tried to compile Merkaartor from SVN on my linux box with Qt4.3.4
and encountered a small problem with compilation - one has to change
QPlainTextEdit widget AboutDialog.ui to QTextEdit because
QPlainTextEdit is available only from Qt4.4.

Apart from this, it compiled and then run fine, good work guys!

Cheers
Martin