Driver: bifurcate extended and basic MSC versioning

This restores the original behaviour of -fmsc-version. The older option
remains as a mechanism for specifying the basic version information. A
secondary option, -fms-compatibility-version permits the user to specify an
extended version to the driver.

The new version takes the value as a dot-separated value rather than the
major * 100 + minor format that -fmsc-version format. This makes it easier to
specify the value as well as a more flexible manner for specifying the value.

Specifying both values is considered an error.

The older parameter is left solely as a driver option, which is normalised into
the newer parameter. This allows us to retain a single code path in the
compiler itself whilst preserving the semantics of the old parameter as well as
avoid having to determine which of two formats are being used by the invocation.

The test changes are due to the fact that the compiler no longer supports the
old option, and is a direct conversion to the new option.