add Steam and chrome to (default) overlay blacklist

Otherwise, Steam as well as chrome (with flash?) get hooked. This will result
in the need to restart them on Mumble updating for example, which is
confusing to users because there is no visible overlay in those applications
anyway.

overlay/overlay_blacklist.h

@@ -60,6 +60,8 @@ static const char *overlayBlacklist[] = {
 	"hlfaceposer.exe", // Face Poser (from Source SDK)
 	"LoLLauncher.exe", // League of Legends Launcher/Patcher
 	"acrobat.exe", // Adobe Acrobat
+	"Steam.exe", // Prevent invisible hooking
+	"chrome.exe", // Prevent invisible hooking (flash?)
 	NULL
 };