Add the vpiFile and vpiLineNo properties to system functions.
Most other objects have stubs that return "N/A"/0. Interactive
functions (called from the debugger) use <interactive> for the
file name.
Modified the code that deals with real variables to accept an integer
value when using vpi_put_value(). Also added some type of diagnostic
message for all switch defaults that have an assert(0) to indicate an
error condition, removed CVS comments and removed a small section of
unreachable code.