Clean last word of target bitset after using Copy.

[steampoweredtaco]

Description

This PR will use the existing cleanLastWord when copying a bitset to keep the invariant other functions depend on, such as Count, that no bits are set past the length of the bitmask on the last uint64 word.

Please include a summary of the changes and the related issue. Please also include relevant motivation and context. List any dependencies that are required for this change.

Fixes #112

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

A new TestCopyUnaligned unit test has been added which verifies that a new bitmask copy that isn't aligned on a 64 bit copies from a bitmask that is larger, but only by less than a uint64 word, that Count and the set bits in the copy are correct. Without the change, this test will fail where the targets Count() would be > than the length of the target.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• (NA) I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• (NA) Any dependent changes have been merged and published in downstream modules

[lemire]

Running tests.

[lemire]

Merging.