From: https://github.com/andersonpd/eris/issues/6

> The ongoing problem with std.bigint is that CTFE is not available for
the 32-bit Windows version. Because of this eris.decimal will not
compile with std.bigint. The fundamental issue is that std.bigint uses
assembly language routines for speed-up in the 32-bit Windows versions
and asm instructions cannot be evaluated at compile time.

I have, as noted, created a separate big integer type which I am sure is
not as fast as std.bigint, but it is correctly implemented. I just hate
to see two different bigint implementations in phobos, so I have not
pushed to move my eris.decimal to std.decimal until std.bigint is modified.