Extend version checking/warnings for checkpoint continuation

Detect if the major/minor versions differ, and write a more
explicit warning that both explains this type of continuation
is unsupported, and recommend to use the -noappend option.
In contrast, for cases where only the patch level differs,
we now only issue a note that the binary has changed, since
this is fully supported.

Fixes #1230.

Change-Id: Ifec509de0e5a05d170ada89fd000c961e311c9ca