Remove unsafe keyword for Platform trait

My guess is that it was unsafe to encourage people to use the platform!
macro, but there is no downside to implementing the trait manually and
often the macro is not flexible enough.  So this patch removes the
unsafe keyword for the Platform trait.

CHANGELOG.md

@@ -63,6 +63,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - Removed the storage types to return `&dyn DynFilesystem` instead.
   - Removed the `Copy` requirement.
   - Removed the `unsafe` keyword for the `Store` trait.
+- Removed the `unsafe` keyword for the `Platform` trait.
 
 ### Fixed
 

src/platform.rs

@@ -54,7 +54,7 @@ pub trait UserInterface {
 // This is the same trick as in "store.rs",
 // replacing generic parameters with associated types
 // and a macro.
-pub unsafe trait Platform {
+pub trait Platform {
     // temporarily remove CryptoRng bound until HALs come along
     type R: CryptoRng + RngCore;
     type S: Store;
@@ -92,7 +92,7 @@ macro_rules! platform {
             }
         }
 
-        unsafe impl $crate::platform::Platform for $PlatformName {
+        impl $crate::platform::Platform for $PlatformName {
             type R = $Rng;
             type S = $Store;
             type UI = $UserInterface;

src/virt.rs

@@ -210,7 +210,7 @@ impl Platform<'_> {
     }
 }
 
-unsafe impl<'a> platform::Platform for Platform<'a> {
+impl<'a> platform::Platform for Platform<'a> {
     type R = ChaCha8Rng;
     type S = store::Store<'a>;
     type UI = UserInterface;