revlog: use proper version comparison during verify
Verify appears to want to compare the changelog's revlog version
number with the version number of filelogs and error if they are
different. But what it was actually doing was comparing the full
32-bit header integer, which contains 2 shorts: 1 for the revlog
version number and 1 for feature flags.
This commit tweaks the verification code so it only looks at the
version number component of the header and emits a warning if they
differ.
The new code is more robust because it accounts for future revlog
version numbers without them needing to be special cased.
Differential Revision: https://phab.mercurial-scm.org/D4704