Chkvpierr

check_vpi_error checks on all VPI calls.


Currently the -DFILTER setting on gpi_logging.c causes all of the mesasges from cocotb.gpi to be suppressed.  If I remove the -DFILTER define, a lot of DEBUG level messages appear as well as the errors from vpi_chk_error

Not sure currently how to control the filtering level on cocotb.gpi messages from the C library to the Python logger.

Would be great if this level was set to INFO or above, then these VPI messages would be visible on bad calls (tested working in VCS with the -DFILTER removed - I see errors when I do bad things over the VPI)

Should help with issue #53 (but not an actual fix, just better visibility on potential issues when they happen)