Initial commit.

This is basically the haskell-bit-integer-experiment codebase from
where I left off debugging it in that tree.
Remove New2 from benchmarking. Perf bug still present.
Remove Check/Common.hs tests.
Purge New4/ tree. Perf bug remains.
Check/NewX.template.hs : Drop non-multiplication tests.

Perf bug remains.
Pare down New1/ implementation.
Pare down New3/ (to match New1/) implementation.
bench-integer.hs : Run New1 and New3 tests multiple times.
Makefile : Add -dump-* command line options.