Naming conventions for export and import members of a struct

[Per Nordlöw]

The integer type in gmp-z just got export (binary serialization) 
support at

https://github.com/nordlow/gmp-d/pull/8

Next up is import (binary deserialization).

What's the preferred D-style naming convention for wrapping 
exporting and exporting to binary formats?

I'm thinking

     Z.to!(U[])

for exporting and

     Z(U[])
or
     Z.from(U[])

for importing but I'm not sure.

Phobos' std.bigint doesn't have any binary serialization so we 
can't mimic that.