Add support for TrueType fonts

* Keeps original font system in place
* Uses the same API as original font system:
   - You can render only one line at a time
   - You can only use one font and color for one gr_text* call
* Caches all rendered text, with a string cache limited to 400
  entries, then it trucates to 250, which results in memory
  usage hovering around 5-10MB

Change-Id: I36107b9dcd8d57bae4486fce8b8f64e49ef3d906
Signed-off-by: Vojtech Bocek <vbocek@gmail.com>
diff --git a/gui/slidervalue.cpp b/gui/slidervalue.cpp
index 5b4d57f..700d7d5 100644
--- a/gui/slidervalue.cpp
+++ b/gui/slidervalue.cpp
@@ -198,7 +198,7 @@
 		}
 	}
 
-	gr_getFontDetails(mFont ? mFont->GetResource() : NULL, (unsigned*) &mFontHeight, NULL);
+	mFontHeight = gr_getMaxFontHeight(mFont ? mFont->GetResource() : NULL);
 
 	if(mShowCurr)
 	{