make GuestAddressSpace require Clone

All of our implementation already provide it, just make it
part of the interface.

Signed-off-by: Paolo Bonzini <[email protected]>

Author: bonzini

CHANGELOG.md

@@ -8,6 +8,7 @@
 - \[[#312](https://github.com/rust-vmm/vm-memory/pull/312)\] `GuestRegionContainer`, a generic container of `GuestMemoryRegion`s, generalizing `GuestMemoryMmap` (which 
   is now a type alias for `GuestRegionContainer<GuestRegionMmap>`).
 - \[[#338](https://github.com/rust-vmm/vm-memory/pull/338)\] Make `GuestMemoryAtomic` always implement `Clone`.
+- \[[#338](https://github.com/rust-vmm/vm-memory/pull/338)\] Make `GuestAddressSpace` a subtrait of `Clone`.
 
 ### Changed
 

src/guest_memory.rs

@@ -219,7 +219,7 @@ impl FileOffset {
 /// # }
 /// # }
 /// ```
-pub trait GuestAddressSpace {
+pub trait GuestAddressSpace: Clone {
     /// The type that will be used to access guest memory.
     type M: GuestMemory;