DRTVWR-476: Eliminate std::mem_fun1() special case for Windows.

We used to have to use #if LL_WINDOWS logic to pass std::mem_fun1() to
llbind2nd() instead of std::mem_fun() elsewhere. VS 2017 no longer supports
std::mem_fun1(), which means we can eliminate the special case for Windows.

indra/newview/llfloaterregioninfo.cpp

@@ -573,11 +573,7 @@ void LLFloaterRegionInfo::refreshFromRegion(LLViewerRegion* region)
 		mInfoPanels.begin(),
 		mInfoPanels.end(),
 		llbind2nd(
-#if LL_WINDOWS
-			std::mem_fun1(&LLPanelRegionInfo::refreshFromRegion),
-#else
 			std::mem_fun(&LLPanelRegionInfo::refreshFromRegion),
-#endif
 			region));
 }