fix MSVC compiler warning

tests/compile/cargdef.pyx

 # mode: compile
 
-def f(obj, int i, float f, char *s1, char s2[]):
+def f(obj, int i, double f, char *s1, char s2[]):
     pass
 
-cdef g(obj, int i, float f, char *s1, char s2[]):
+cdef g(obj, int i, double f, char *s1, char s2[]):
     pass
 
-cdef do_g(object (*func)(object, int, float, char*, char*)):
+cdef do_g(object (*func)(object, int, double, char*, char*)):
     return func(1, 2, 3.14159, "a", "b")
 
 do_g(&g)