fixedbitset

Optimized the Clone::clone_from implementation to avoid allocations and redundant copies.

Fixed FixedBitset not implementing Send/Sync due to the stack size shrink.

• #116: Add functions for counting the results of a set operation (union_count,
  intersection_count, difference_count, symmetric_difference_count) by @james7132.
• #118: Shrink the stack size of FixedBitset. There should be zero stack size overhead
  compared to a Vec.
• #119: Fix builds for wasm32.
• #120: Add more utility functions that were previously missing from the public interface:
  contains_any_in_range, contains_all_in_range, minimum, maximum, is_full, count_zeroes, and remove_range.
• #121: Add support for SIMD acceleration for AVX builds.

#112: Fix undefined behavior in IntoOnes and setup testing with MIRI by @SkiFire13

#109: Fix non-x86(_64) builds by @james7132

• #86: Explicit SIMD vectorization for set operations by @james7132.

• #102: Added contains_unchecked, insert_unchecked, put_unchecked,
  set_unchecked, toggle_unchecked, removed_unchecked, copy_bit_unchecked unsafe variants of the safe functions, by @james7132
• #103: Added into_ones which returns a owned iterator over the one
  values from a bitset, by @james7132.
• #104: Implemented DoubleEndedIterator for Union, Intersection,
  Difference, and SymmetricDifference , by @james7132.

#79: Add is_clear, clarify is_empty and len documentation by @nicopap.

Documentation and formatting fixes.