Bump version number to 1.2.0.6
Add flag to control use of SSE 2, as for SSE 4.1.
Bump version number to 1.2.0.7
Fix linking with the sse2 flag unset.

The patch adding the sse2 flag allowed hashable to build on systems
without the appropriate SSE symbols available, but didn't allow linking,
as the resulting code still referenced one of the internal symbols from
the SSE2 implementation. This patch fixes that.
Bump cabal version to 1.2.0.8.
Handle signed size parameter of J# constructor correctly

This fixes bug #68.