textbox: don't accept boxes with no borderwidth

Origin commit data
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Commit: 050df14f8d
Author: vanhofen <vanhofen@gmx.de>
Date: 2013-05-08 (Wed, 08 May 2013)

Origin message was:
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- textbox: don't accept boxes with no borderwidth

src/gui/widget/textbox.cpp

@@ -220,7 +220,10 @@ void CTextBox::setTextFont(Font* font_text)
 
 void CTextBox::setTextBorderWidth(int border)
 {
-	text_border_width = border;
+	/* we need a minimal borderwith of 1px because the edge-smoothing
+	(or fontrenderer?) otherwise will paint single pixels outside the
+	defined area. e.g. 'j' is leaving such residues */
+	text_border_width = (border > 0) ? border : 1;
 	//Initialise the window frames first and than refresh text line array
 	initFramesAndTextArray();
 }