Fixed reading multiple images from ANI and ICO image files.

Fixed reading multiple images from ANI and ICO image files.

In r60852 various 'unneeded' SeekI(0) calls were removed. Examined the changes in that revision and restored all SeekI(0) calls after finding out their removal caused problems with reading more than one image from ICO and ANI files. The image handling code for these formats expects to read from the start of a stream for reading its images (as well as for DoCanRead and DoGetImageCount), regardless of the index of the requested image.

Closes #12861.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67671 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775