add cli option `-v/--version`

doc/usage.md

@@ -32,6 +32,7 @@ The miner allow to overwrite some of the settings via command line options.
 Usage: xmr-stak [OPTION]...
 
   -h, --help            show this help
+  -v, --version         show version number
   -c, --config FILE     common miner configuration file
   --currency NAME       currency to mine: monero or aeon
   --noCPU               disable the CPU miner backend

xmrstak/cli/cli-miner.cpp

@@ -63,6 +63,7 @@ void help()
 	cout<<"Usage: "<<params::inst().binaryName<<" [OPTION]..."<<endl;
 	cout<<" "<<endl;
 	cout<<"  -h, --help            show this help"<<endl;
+	cout<<"  -v, --version         show version number"<<endl;
 	cout<<"  -c, --config FILE     common miner configuration file"<<endl;
 #if (!defined(CONF_NO_AEON)) && (!defined(CONF_NO_MONERO))
 	cout<<"  --currency NAME       currency to mine: monero or aeon"<<endl;
@@ -296,6 +297,11 @@ int main(int argc, char *argv[])
 			//win_exit();
 			return 0;
 		}
+		if(opName.compare("-v") == 0 || opName.compare("--version") == 0)
+		{
+			std::cout<< "Version: " << get_version_str() << std::endl;
+			return 0;
+		}
 		else if(opName.compare("--noCPU") == 0)
 		{
 			params::inst().useCPU = false;