Fix behaviour of IV after closing an image
Fix behaviour of IV after closing an image

current_image (int) setter thought the new image index was equal to the
last one, so it refused to change it. Now, the last image index is
modified accordingly.

Change current_image() to m_current_image at the bottom closeImg() to prevent
ambiguity. Don't use current_image() setter, as it complicates things
too much in this case.

sambler/oiio,OpenImageIO/oiio,cwilling/oiio,YangYangTL/oiio,OpenImageIO/oiio,lgritz/oiio,bdeluca/oiio,mcanthony/oiio,scott-wilson/oiio,jeremyselan/oiio,cwilling/oiio,mcanthony/oiio,cwilling/oiio,mcanthony/oiio,YangYangTL/oiio,micler/oiio,sambler/oiio,bdeluca/oiio,YangYangTL/oiio,sambler/oiio,micler/oiio,jeremyselan/oiio,bdeluca/oiio,bdeluca/oiio,jeremyselan/oiio,scott-wilson/oiio,cwilling/oiio,sambler/oiio,micler/oiio,YangYangTL/oiio,micler/oiio,lgritz/oiio,OpenImageIO/oiio,OpenImageIO/oiio,scott-wilson/oiio,lgritz/oiio,scott-wilson/oiio,lgritz/oiio,mcanthony/oiio