Wave scattering in sea ice incorrectly coded for IS1 option

[cmbitz]

Describe the bug
The IS1 option calls a subroutine that returns a source term VSIR, but VSIR is never used. It does not return a "diagonal" term VDIR, though VDIR would be correctly used if it had. The relevant code is

    CALL W3SIS1 ( SPEC, ICE, VSIR )
    ATT=ATT*EXP(ICE*VDIR(IS)*DTG)

To Reproduce
Do a run where W3_IS1 is defined and compare it to a run without defining W3_IS1. The output will be bit-for-bit the same.

Expected behavior
What should happen is that IS1 scattering dampens wave energy in the sea ice.

Screenshots
N/A

Additional context
I haven't tried to fix this, but I know how to do it. I'm not interested in using this option myself. However, I think some people do use IS1, and may not realize it does nothing. I'd like to also mention this bug is unrelated to the other issue (#1294) that we have about numerical solutions involving sea ice. #1294 is not a bug, but rather a recommendation to improve the numerics. This is plainly a bug. I'd be happy to provide a pull request with this fix combined with correction to the numerics that I am recommending in issue #1294