Add float.__ceil__ and __floor__

Closes: python#3195

Author: srittau

stdlib/2/__builtin__.pyi

@@ -265,6 +265,9 @@ class float:
     def __rpow__(self, x: float, mod: None = ...) -> float: ...
     def __getnewargs__(self) -> Tuple[float]: ...
     def __trunc__(self) -> int: ...
+    if sys.version_info >= (3, 9):
+        def __ceil__(self) -> int: ...
+        def __floor__(self) -> int: ...
     if sys.version_info >= (3,):
         @overload
         def __round__(self, ndigits: None = ...) -> int: ...

stdlib/2and3/builtins.pyi

@@ -265,6 +265,9 @@ class float:
     def __rpow__(self, x: float, mod: None = ...) -> float: ...
     def __getnewargs__(self) -> Tuple[float]: ...
     def __trunc__(self) -> int: ...
+    if sys.version_info >= (3, 9):
+        def __ceil__(self) -> int: ...
+        def __floor__(self) -> int: ...
     if sys.version_info >= (3,):
         @overload
         def __round__(self, ndigits: None = ...) -> int: ...