[Editor] Add "--debug-server <uri>" option.

Allow starting the editor debugger server for the given protocol (and
optionally bound to the given ip/port combination:

godot -e --debug-server tcp://*:8080

main/main.cpp

@@ -145,6 +145,7 @@ static bool auto_quit = false;
 static OS::ProcessID allow_focus_steal_pid = 0;
 #ifdef TOOLS_ENABLED
 static bool auto_build_solutions = false;
+static String debug_server_uri;
 #endif
 
 // Display
@@ -286,6 +287,7 @@ void Main::print_help(const char *p_binary) {
 #ifdef TOOLS_ENABLED
 	OS::get_singleton()->print("  -e, --editor                                 Start the editor instead of running the scene.\n");
 	OS::get_singleton()->print("  -p, --project-manager                        Start the project manager, even if a project is auto-detected.\n");
+	OS::get_singleton()->print("  --debug-server <uri>                         Start the editor debug server (<protocol>://<host/IP>[:<port>], e.g. tcp://127.0.0.1:6007)\n");
 #endif
 	OS::get_singleton()->print("  -q, --quit                                   Quit after the first iteration.\n");
 	OS::get_singleton()->print("  -l, --language <locale>                      Use a specific locale (<locale> being a two-letter code).\n");
@@ -874,6 +876,18 @@ Error Main::setup(const char *execpath, int argc, char *argv[], bool p_second_ph
 		} else if (I->get() == "-p" || I->get() == "--project-manager") { // starts project manager
 
 			project_manager = true;
+		} else if (I->get() == "--debug-server") {
+			if (I->next()) {
+				debug_server_uri = I->next()->get();
+				if (debug_server_uri.find("://") == -1) { // wrong address
+					OS::get_singleton()->print("Invalid debug server uri. It should be of the form <protocol>://<bind_address>:<port>.\n");
+					goto error;
+				}
+				N = I->next()->next();
+			} else {
+				OS::get_singleton()->print("Missing remote debug server uri, aborting.\n");
+				goto error;
+			}
 		} else if (I->get() == "--build-solutions") { // Build the scripting solution such C#
 
 			auto_build_solutions = true;
@@ -2346,6 +2360,9 @@ bool Main::start() {
 					}
 				}
 				DisplayServer::get_singleton()->set_context(DisplayServer::CONTEXT_EDITOR);
+				if (!debug_server_uri.is_empty()) {
+					EditorDebuggerNode::get_singleton()->start(debug_server_uri);
+				}
 			}
 #endif
 			if (!editor) {