MOAIFreeTypeFont: Added missing resource creation and clean up code in DimensionsWithMaxWidth

Previously, these were only initialized inside `RenderTexture()`, but they are also needed in any other externally accessible methods that call `WidthOfString()`.

You should assert `mGlyphArray` and `mAdvanceArray` are actually `NULL` here, to avoid the leak and the potential bug in case they are actually being overridden.