ImageCache invalidation fix: the mod_time of the file should be recorded in open(), not in the ImageCacheFile constructor.
ImageCache invalidation fix: the mod_time of the file should be recorded
in open(), not in the ImageCacheFile constructor.

If recorded in the ctr and subsequently invalidated, closed, file
modified, then re-opened... it still never reset the recorded time.  So
later calls to invalidate_all would always invalidate the file and flush
all its tiles, even though the file wasn't modified again.



git-svn-id: c3edda122e248ef33995da003806c930f62b9468@1712 31904243-a364-42ac-a3db-9305396518ba

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