Remove old isnan isfinite hack

indra/llmath/llmath.h

@@ -42,18 +42,8 @@
 // llcommon depend on llmath.
 #include "is_approx_equal_fraction.h"
 
-// work around for Windows & older gcc non-standard function names.
-#if LL_WINDOWS
-#include <float.h>
-#define llisnan(val)	_isnan(val)
-#define llfinite(val)	_finite(val)
-#elif (LL_LINUX && __GNUC__ <= 2)
-#define llisnan(val)	isnan(val)
-#define llfinite(val)	isfinite(val)
-#else
 #define llisnan(val)	std::isnan(val)
 #define llfinite(val)	std::isfinite(val)
-#endif
 
 // Single Precision Floating Point Routines
 // (There used to be more defined here, but they appeared to be redundant and