2024: Add unsafe attribute differences

Author: ehuss

src/abi.md

@@ -74,6 +74,8 @@ with the same name (or with a well-known symbol), leading to undefined behavior.
 extern "C" fn foo() {}
 ```
 
+> **Edition Differences**: Before the 2024 edition it is allowed to use the `no_mangle` attribute without the `unsafe` qualification.
+
 ## The `link_section` attribute
 
 The *`link_section` attribute* specifies the section of the object file that a
@@ -90,6 +92,8 @@ of memory not expecting them, such as mutable data into read-only areas.
 pub static VAR1: u32 = 1;
 ```
 
+> **Edition Differences**: Before the 2024 edition it is allowed to use the `link_section` attribute without the `unsafe` qualification.
+
 ## The `export_name` attribute
 
 The *`export_name` attribute* specifies the name of the symbol that will be
@@ -105,6 +109,8 @@ behavior.
 pub fn name_in_rust() { }
 ```
 
+> **Edition Differences**: Before the 2024 edition it is allowed to use the `export_name` attribute without the `unsafe` qualification.
+
 [_MetaNameValueStr_]: attributes.md#meta-item-attribute-syntax
 [`static` items]: items/static-items.md
 [attribute]: attributes.md