Removed support for multi-line text drawing

When trying to test the previous commit, I couldn't find any place in
the application where strings containing newlines are drawn. So I'm
assuming this is an unnecessary feature, until someone comes up with
a test case proving otherwise.

Yeah, I'm too lazy to review all the code that draws text...

src/font.h

@@ -41,9 +41,6 @@ public:
 private:
 	Font(TTF_Font *font);
 
-	void writeLine(Surface *surface, std::string const& text,
-				int x, int y, HAlign halign, VAlign valign);
-
 	TTF_Font *font;
 	int lineSpacing;
 };