This patch modifies the conversion functions $rtoi, $itor,
$realtobits and $bitstoreal calltf routines to be more efficient.
This is done by caching the vpiHandle to the argument in the userdata
pointer. This eliminated the need to get the argument iterator, scan
and free the iterator.
It also updates the error messages to use the new file and line
number information that is available for system functions. It also
adds a check that verifies the functions are only called with one
argument and makes the errors fatal.