Changelog entry.

Changelog.md

@@ -3,6 +3,7 @@
 How to update your code:
  * Change every ``.call()`` to a ``.call("")`` and every ``.call(signature, a, b, c)`` to use ``.call(abi.encodeWithSignature(signature, a, b, c))`` (the last one only works for value types).
  * Change every ``keccak256(a, b, c)`` to ``keccak256(abi.encodePacked(a, b, c))``.
+ * Make your fallback functions ``external``.
 
 
 Breaking Changes:
@@ -28,6 +29,7 @@ Breaking Changes:
  * Type Checker: Disallow arithmetic operations for boolean variables.
  * Type Checker: Disallow conversions between ``bytesX`` and ``uintY`` of different size.
  * Type Checker: Only accept a single ``bytes`` type for ``.call()`` (and family), ``keccak256()``, ``sha256()`` and ``ripemd160()``.
+ * Type Checker: Fallback function must be external. This was already the case in the experimental 0.5.0 mode.
  * Remove obsolete ``std`` directory from the Solidity repository. This means accessing ``https://github.com/ethereum/soldity/blob/develop/std/*.sol`` (or ``https://github.com/ethereum/solidity/std/*.sol`` in Remix) will not be possible.
  * Syntax Checker: Named return values in function types are an error.