Merge pull request #396 from anntzer/signbit

Add signbit to math.pxd.

Cython/Includes/libc/math.pxd

@@ -95,8 +95,9 @@ cdef extern from "math.h" nogil:
     double scalbn(double x, int n)
 
     double nan(const char*)
-    
+
     bint isfinite(long double)
-    bint isnormal(long double)
-    bint isnan(long double)
     bint isinf(long double)
+    bint isnan(long double)
+    bint isnormal(long double)
+    bint signbit(long double)