Texturefont glyphplacements

Some minor modifications to TextureFont's glyphPlacements methods - fixed size bug in the clipping variant and added a one for caching wrapped placements, such as:

```
// in setup()...
mCachedGlyphMeasures = mTextureFont->getGlyphPlacementsWrapped( "Hi Hi", mTextBounds );

// in draw()...
mTextureFont->drawGlyphs( mCachedGlyphMeasures, mTextBounds.getUpperLeft() );
```