Implement semantic analysis of @staticmethod
Basic type checking of static methods
Add staticmethod test case
Add staticmethod to builtins stubs
Add int methods to stubs

We use a static from_bytes method, because class methods haven't been
implemented, but this is slightly wrong.
Fixes to test cases
Add float methods to stubs

Note that float.fromhex is a static method even though it should
really be a class method.
Add staticmethod to 2.7 builtins stubs
Stub fixes
Fixes to array stubs