Remove Copy impl on internal types

Cargo.toml

@@ -8,7 +8,7 @@ documentation = "http://bsago.me/doc/users/"
 homepage = "https://github.com/ogham/rust-users"
 license = "MIT"
 readme = "README.md"
-version = "0.3.1"
+version = "0.3.2"
 
 [dependencies]
 libc = "0.1.1"

src/lib.rs

@@ -163,8 +163,6 @@ struct c_passwd {
     pub pw_expire:  time_t,         // password expiry time
 }
 
-impl Copy for c_passwd { }
-
 #[repr(C)]
 struct c_group {
     pub gr_name:   *const c_char,         // group name
@@ -173,8 +171,6 @@ struct c_group {
     pub gr_mem:    *const *const c_char,  // names of users in the group
 }
 
-impl Copy for c_group { }
-
 extern {
     fn getpwuid(uid: c_int) -> *const c_passwd;
     fn getpwnam(user_name: *const c_char) -> *const c_passwd;