Move contents of builtins/* to stdlib/*. This simplifies finding stubs.

stdlib/2and3/math.pyi

@@ -0,0 +1,52 @@
+# Stubs for math
+# See: http://docs.python.org/2/library/math.html
+
+from typing import Tuple, Iterable, Optional
+
+import sys
+
+e = ...  # type: float
+pi = ...  # type: float
+
+def acos(x: float) -> float: ...
+def acosh(x: float) -> float: ...
+def asin(x: float) -> float: ...
+def asinh(x: float) -> float: ...
+def atan(x: float) -> float: ...
+def atan2(y: float, x: float) -> float: ...
+def atanh(x: float) -> float: ...
+def ceil(x: float) -> int: ...
+def copysign(x: float, y: float) -> float: ...
+def cos(x: float) -> float: ...
+def cosh(x: float) -> float: ...
+def degrees(x: float) -> float: ...
+def erf(x: float) -> float: ...
+def erfc(x: float) -> float: ...
+def exp(x: float) -> float: ...
+def expm1(x: float) -> float: ...
+def fabs(x: float) -> float: ...
+def factorial(x: int) -> int: ...
+def floor(x: float) -> float: ...
+def fmod(x: float, y: float) -> float: ...
+def frexp(x: float) -> Tuple[float, int]: ...
+def fsum(iterable: Iterable) -> float: ...
+def gamma(x: float) -> float: ...
+def hypot(x: float, y: float) -> float: ...
+def isinf(x: float) -> bool: ...
+if sys.version_info[0] >= 3:
+    def isfinite(x: float) -> bool: ...
+def isnan(x: float) -> bool: ...
+def ldexp(x: float, i: int) -> float: ...
+def lgamma(x: float) -> float: ...
+def log(x: float, base: float = ...) -> float: ...
+def log10(x: float) -> float: ...
+def log1p(x: float) -> float: ...
+def modf(x: float) -> Tuple[float, float]: ...
+def pow(x: float, y: float) -> float: ...
+def radians(x: float) -> float: ...
+def sin(x: float) -> float: ...
+def sinh(x: float) -> float: ...
+def sqrt(x: float) -> float: ...
+def tan(x: float) -> float: ...
+def tanh(x: float) -> float: ...
+def trunc(x: float) -> int: ...