Bit blit routine, version 1

[Niels Möller]

Torbjorn Granlund <tg at swox.com> writes:

> Please explain what you mean with bit-blit.

A bitblit operates on a substrings of bitstrings. For example, the
1000 bits starting at bit 17 of some given 100-limb number.

If I understood the code correctly, the only operation so far is
copying, but it could be generalized to n source operands and a
selection of any of the 2^(2^n) possible boolean functions. The
Amiga's blitter hardware used n = 3, and handled rectangular subsets
of bitmaps.

/Niels