Use the new cur_instance variable to get the call handle instead of calling
vpi_handle(vpiSysTfCall, 0).
This completes a proper fix for issue #141, to replace the problematic fix
that was reverted in commit 8da8261f.
acc_ functions. Add support for standard ACC
string handling.
Add the _pli_types.h header file to carry the
IEEE1364-2001 standard PLI type declarations.