Merge pull request #872 from bmatthewshea/master

--list-devices -> add -X

ethminer/MinerAux.h

@@ -670,7 +670,7 @@ class MinerCLI
 			<< "    --opencl-device <n>  When mining using -G/--opencl use OpenCL device n (default: 0)." << endl
 			<< "    --opencl-devices <0 1 ..n> Select which OpenCL devices to mine on. Default is to use all" << endl
 			<< "    -t, --mining-threads <n> Limit number of CPU/GPU miners to n (default: use everything available on selected platform)" << endl
-			<< "    --list-devices List the detected OpenCL/CUDA devices and exit. Should be combined with -G or -U flag" << endl
+			<< "    --list-devices List the detected OpenCL/CUDA devices and exit. Should be combined with -G, -U, or -X flag" << endl
 			<< "    --display-interval <n> Set mining stats display interval in seconds. (default: every 5 seconds)" << endl			
 			<< "    -L, --dag-load-mode <mode> DAG generation mode." << endl
 			<< "        parallel    - load DAG on all GPUs at the same time (default)" << endl