This fixes a bug in --export bgen-1.{2,3}'s behavior on chrX and chrY, where data for the last few samples might not be properly exported (possibly resulting in an invalid .bgen).
In addition:
- "requires an alpha 6 or later build" error messages are now printed when appropriate.
- The version string has been reformatted to adhere to the Semantic Versioning 2.0.0 spec.
- The --lax-bgen-import flag has been backported.