NumberDate: remove unnecessary definitions of isnan, isinf

These are provided by the Microsoft C Runtime, no need to define them
anymore.

Author: compnerd

Diff for: CoreFoundation/NumberDate.subproj/CFNumber.c

@@ -75,8 +75,6 @@ static const uint8_t __CFNumberCanonicalTypeIndex[] = {
 
 
 #if DEPLOYMENT_TARGET_WINDOWS
-#define isnan(A) _isnan(A)
-#define isinf(A) !_finite(A)
 #define copysign(A, B) _copysign(A, B)
 #endif