Rip out old workarounds, hacks and macros for newer C++ features not being supported back in the day.

Adds LL_COMPILE_TIME_MESSAGE support to Linux.

llfinite -> std::isfinite
llisnan -> std::isnan
vector_shrink_to_fit -> vector.shrink_to_fit

indra/llmath/v3math.cpp

@@ -76,7 +76,7 @@ BOOL LLVector3::clampLength( F32 length_limit )
 	BOOL changed = FALSE;
 
 	F32 len = length();
-	if (llfinite(len))
+	if (std::isfinite(len))
 	{
 		if ( len > length_limit)
 		{
@@ -97,7 +97,7 @@ BOOL LLVector3::clampLength( F32 length_limit )
 		for (S32 i = 0; i < 3; ++i)
 		{
 			F32 abs_component = fabs(mV[i]);
-			if (llfinite(abs_component))
+			if (std::isfinite(abs_component))
 			{
 				if (abs_component > max_abs_component)
 				{