swift234

Clang importer: use lookup table version number in the module file extension hash.

We were verifying the Swift full version information from the module
file extension metadata for the Swift name lookup tables, but not
actually putting it in the hash, which meant that having an older
module cache around would cause spurious failures when Swift name
lookup tables were enabled. Instead, use just the major/minor version
numbers of the lookup tables. When the lookup table format or contents
of the lookup table change, we'll bump the version number.