ffi/com: repairs, including `mysterx' compatibility

Restore MysterX-style handling of parameterzied properties in
`com-get-property'.  It turns out that the original `com-get-property'
handles parameterized properties by allowing a list in place of a
property-name string, and that handling got lost in the re-write.

Fix the name of `com-get-active-from-from-coclass'.

Fix arity checking for optional arguments.

Closes PR 13603
Closes PR 13604