Revised fix for bug 3111 - switch to usrt4_0.lib, which is exported unconditionally usrt3_1.lib is invisibly exported by an FLM, so in platform builds this failed with "No rule to make usrt3_1.dso"

EXPORTS
	?WhichDLL@@YAHXZ @ 1 NONAME ; int __cdecl WhichDLL(void)