UI: Add memory usage to Stats window on linux/mac

Closes jp9000/obs-studio#953

UI/platform-windows.cpp

@@ -30,7 +30,6 @@ using namespace std;
 #include <shellapi.h>
 #include <shlobj.h>
 #include <Dwmapi.h>
-#include <psapi.h>
 #include <mmdeviceapi.h>
 #include <audiopolicy.h>
 
@@ -264,17 +263,6 @@ bool DisableAudioDucking(bool disable)
 	return SUCCEEDED(result);
 }
 
-uint64_t CurrentMemoryUsage()
-{
-	PROCESS_MEMORY_COUNTERS pmc = {};
-	pmc.cb = sizeof(pmc);
-
-	if (!GetProcessMemoryInfo(GetCurrentProcess(), &pmc, sizeof(pmc)))
-		return 0;
-
-	return (uint64_t)pmc.WorkingSetSize;
-}
-
 struct RunOnceMutexData {
 	WinHandle handle;