Make delete_blacklisted delete symlinks
Make delete_blacklisted delete symlinks

As discovered in TheAssassin/redeclipse-appimage#3, `delete_blacklisted` does
not delete symlinks to the real `*.so` files. This can cause issues when
an AppImage wants to use the precompiled libraries from a distribution like
Debian which uses symlinks to point to a specific version of a library.

This commit fixes `delete_blacklisted`'s behavior to delete such symlinks.

It is subject to further discussions whether to make the filenames in
`excludelist` wildcards to delete both the symlinks and the files they point
to.
Another approach would be using `readlink -f` to properly resolve the symlinks
and delete their targets. This way one does not have to trust on a wildcard,
although it is very unlike that the globs would delete anything but related
shared object files.

darealshinji/AppImages,probonopd/AppImages