move cmath.pyi into 2and3

builtins/2and3/cmath.pyi

@@ -0,0 +1,30 @@
+"""Stub file for the 'cmath' module."""
+
+from typing import Union
+
+e = ...  # type: float
+pi = ...  # type: float
+
+_C = Union[float, complex]
+
+def acos(x:_C) -> complex: ...
+def acosh(x:_C) -> complex: ...
+def asin(x:_C) -> complex: ...
+def asinh(x:_C) -> complex: ...
+def atan(x:_C) -> complex: ...
+def atanh(x:_C) -> complex: ...
+def cos(x:_C) -> complex: ...
+def cosh(x:_C) -> complex: ...
+def exp(x:_C) -> complex: ...
+def isinf(z:_C) -> bool: ...
+def isnan(z:_C) -> bool: ...
+def log(x:_C, base:_C = ...) -> complex: ...
+def log10(x:_C) -> complex: ...
+def phase(z:_C) -> float: ...
+def polar(z:_C) -> Tuple[float, float]: ...
+def rect(r:float, phi:float) -> complex: ...
+def sin(x:_C) -> complex: ...
+def sinh(x:_C) -> complex: ...
+def sqrt(x:_C) -> complex: ...
+def tan(x:_C) -> complex: ...
+def tanh(x:_C) -> complex: ...