This patch adds $simparam and $simparam$str from Verilog-A.
The analog simulator parameters return 0.0 or N/A. The
vvp_cpu_wordsize system function has been moved into the
$simparam call and is now named CPUWordSize.
This patch also starts the factoring of common code in the
vpi directory. Some routines were renamed.
The priv.c file was renamed to sys_priv.c to match the
include file.
System functions can now have strings put to their output.