Add protype of LrHandleMirrorFailureCb
yum: Add Mirror Failure Callback Data structure and functions (mfcbdata_*)
API CHANGE: Removed cbdata param from lr_download_single_cb(). Use specific data for each target.
API CHANGE: lr_download_single_cb() new param mfcb (LrMirrorFailureCb)
Handle: Add LRO_HMFCB and LRI_HMFCB options.
Yum: Add support for LRO_HMFCB
Python: Add support for LRO_HMFCB and LRI_HMFCB
Doc: Update python doc
Downloader: If checksums don't match, include the expected values and types in the error message.