Efficient arrays of booleans

This library provides an object type which efficiently represents an
array of booleans. Bitarrays are sequence types and behave very much
like usual lists. Eight bits are represented by one byte in a
contiguous block of memory. The user can select between two
representations: little-endian and big-endian. All functionality is
implemented in C. Methods for accessing the machine representation are
provided, including the ability to import and export buffers. This
allows creating bitarrays that are mapped to other objects, including
memory-mapped files.
