Fix constants in libc/math.pxd

Cython/Includes/libc/math.pxd

 cdef extern from "math.h" nogil:
 
-    enum: M_E
-    enum: M_LOG2E
-    enum: M_LOG10E
-    enum: M_LN2
-    enum: M_LN10
-    enum: M_PI
-    enum: M_PI_2
-    enum: M_PI_4
-    enum: M_1_PI
-    enum: M_2_PI
-    enum: M_2_SQRTPI
-    enum: M_SQRT2
-    enum: M_SQRT1_2
+    double M_E
+    double M_LOG2E
+    double M_LOG10E
+    double M_LN2
+    double M_LN10
+    double M_PI
+    double M_PI_2
+    double M_PI_4
+    double M_1_PI
+    double M_2_PI
+    double M_2_SQRTPI
+    double M_SQRT2
+    double M_SQRT1_2
 
     double acos(double x)
     double asin(double x)

tests/compile/libc_math.pyx

-# mode: compile
-
 from libc.math cimport (M_E, M_LOG2E, M_LOG10E, M_LN2, M_LN10, M_PI, M_PI_2,
         M_PI_4, M_1_PI, M_2_PI, M_2_SQRTPI, M_SQRT2, M_SQRT1_2)
 from libc.math cimport (acos, asin, atan, atan2, cos, sin, tan, cosh, sinh,
         tanh, acosh, asinh, atanh, exp, log, log10, pow, sqrt)
+
+def test_pi():
+    """
+    >>> import math
+    >>> test_pi() == math.pi
+    True
+    """
+    return M_PI
+
+def test_sin(x):
+    """
+    >>> test_sin(0)
+    0.0
+    >>> from math import sin
+    >>> [sin(k) == test_sin(k) for k in range(10)]
+    [True, True, True, True, True, True, True, True, True, True]
+    """
+    return sin(x)