racket/gui cocoa: fix `list-box%' visble-cell calculations

There were especially problems with header columns, but
also intercell spacing was not taken into account.

Merge to v5.3.4
(cherry picked from commit 44d59702c0b22624f8e0043ccf1c5e4f90ed9c4b)
ffi/com: repairs for parameterized-property setting and for date values

Merge to v5.3.4
(cherry picked from commit 25ddfcbfb3a85e26c786d1f3687acde0f70804e9)