texturec: Fixed PTC14 encoder. Issue #699.

tools/texturec/texturec.cpp

@@ -117,7 +117,7 @@ namespace bgfx
 		case TextureFormat::PTC14:
 			{
 				using namespace Javelin;
-				RgbBitmap bmp;
+				RgbaBitmap bmp;
 				bmp.width  = _width;
 				bmp.height = _height;
 				bmp.data   = (uint8_t*)const_cast<void*>(_src);