64-bit support

[DAVe3283]

There is no 64-bit support added to the Visual Studio solutions by default.
This appears to be because the code is a mess in a 64-bit configuration.

There is lots of non-standard stuff going on (implicit casts of void* to struct pointers, signed/unsigned comparison mismatch, etc) that works OK on 32-bit (but still not right, IMO).

In a 64-bit compile, however, we get many hundreds of warnings. A cursory glance indicates the security code compiles clean, but that will need verified.
And even then, all the warnings should be addressed, since implicit casts and signed/unsigned comparisons can be security flaws in certain situations.

(This might be taken care of in Ice IV's patches)