Added right_control and left_control to key flags as well as right_shift

This is to fix the bug in #261 . Haven't tested it yet since I don't have a working environment yet, but I cannot find anything in the platform documentations that specify a left or right control mask different from the mask that is currently assigned to `MOD_CONTROL` in `keypress.h`. 

Oh, and this also extends the functionality to `right_shift` as well

Author: Deathnerd

src/robotjs.cc

@@ -419,11 +419,11 @@ int CheckKeyFlags(char* f, MMKeyFlags* flags)
 	{
 		*flags = MOD_META;
 	}
-	else if(strcmp(f, "control") == 0)
+	else if(strcmp(f, "control") == 0 || strcmp(f, "right_control") == 0 || strcmp(f, "left_control") == 0)
 	{
 		*flags = MOD_CONTROL;
 	}
-	else if(strcmp(f, "shift") == 0)
+	else if(strcmp(f, "shift") == 0 || strcmp(f, "right_shift") == 0)
 	{
 		*flags = MOD_SHIFT;
 	}