cleanup: internal image information is now unsigned.

cleanup: internal image information is now unsigned.

There is no meaning in negative values for image loading, marking as
dirty or size, so image internals (cache, entry) were changed to
unsigned, reducing possible errors, particularly with overflow.

engines were converted to the new way, but any 3rd party modules will
still work as they should be using values >= 0 only anyway.

please review.

new cases introduced by "comparison between signed and unsigned" were
fixed in the modules that used cache_entry or Image_Entry dimensions.

git-svn-id: svn+ssh://svn.enlightenment.org/var/svn/e/trunk/evas@52428 7cbeb6ba-43b4-40fd-8cce-4c39aea84d33