Add try_get_steam_client().

This allows the emulator to attempt to access the global steam_client object
without creating it if it doesn't exist.

dll/dll.cpp

@@ -140,6 +140,16 @@ Steam_Client *get_steam_client()
     return steamclient_instance;
 }
 
+Steam_Client *try_get_steam_client()
+{
+    Steam_Client * ret = NULL;
+    if (global_mutex.try_lock() == true) {
+        ret = steamclient_instance;
+        global_mutex.unlock();
+    }
+    return ret;
+}
+
 void destroy_client()
 {
     std::lock_guard<std::recursive_mutex> lock(global_mutex);

dll/dll.h

@@ -93,6 +93,7 @@ class GB_CCallbackInterImp : protected CCallbackBase
 
 Steam_Client *get_steam_client();
 bool steamclient_has_ipv6_functions();
+Steam_Client *try_get_steam_client();
 
 HSteamUser flat_hsteamuser();
 HSteamPipe flat_hsteampipe();