Rename some methods and variables

Rename some methods and variables
* styles -> drawstyleHandles
* styles_lastit -> drawstyleHandles_lastit
* styles_lastit_valid -> drawstyleHandles_lastit_valid
* styles_ref -> drawstyleHandlesRefCounts
* styles_ref_lastit -> drawstyleHandlesRefCounts_lastit
* styles_ref_lastit_valid -> drawstyleHandlesRefCounts_lastit_valid
* getStyleRef -> getDrawStyleHandle
* destroyStyleRef -> destroyDrawStyleHandle
* createStyleRef -> createDrawStyleHandle
* incrementStyleRefCount -> incrementDrawStyleHandleRefCount
* decrementStyleRefCount -> decrementDrawStyleHandleRefCount