Icarus verilog v11

[quark17]

As B-Lang-org/bsc-testsuite#16 (and related PR B-Lang-org/bsc-testsuite#17) show, the way that BSC invokes iverilog for designs with imported foreign functions leads to this warning message:

SFT files are deprecated. Please pass the VPI module instead.

I suspect that the bsc_build_vsim_iverilog script in BSC will need to be updated to check the iverilog version and to use different VPI arguments when the version is 11. This should be simple to fix, but it requires figuring out what the new invocation should look like -- so I've marked this as a "good first issue".

In the testsuite, in bsc.options, the exp-file was updated to filter out this deprecation warning (which was otherwise causing a failure when comparing the expected output). This filtering can be removed when the exec script is fixed.

There are also a number of places in the testsuite where we expect verilog tests to fail, for certain versions of iverilog, due to bugs in the VPI support. It would be good to check to whether any of these bugs have been fixed and can be enabled when the iverilog version is 11.