Joining registers for a local variable

[astrelsky]

I have a far pointer which the decompiler sees as a near pointer (See #2751). I would like to be able to tell the decompiler that the variable is actually the combination of the register it currently sees and the register used for the segment portion of the pointer. I've searched through the compiler_spec specifications looking for a way to define locals that are joined pieces of registers like in pentry but to no avail. Is there currently any way to do this?