Fixed and floating point packages

[David Bishop]

I took some time to updated the VHDL-93 compatible source code for the
Fixed and floating point packages:

http://www.vhdl.org/fphdl

I also created a FAQ for these packages:

http://www.vhdl.org/fphdl/fpfaq.html

If I missed something, please let me know.

These are in the new Modelsim Beta (I tested them).