Partial revert: Only make --arg=value fulfill optional arguments.

Otherwise, it's too confusing that flag arguments now consume maybe-unrelated place arguments.

src/std/argparse.nt

@@ -190,18 +190,18 @@ unittest
 unittest
 {
     auto parser = new GccArgParser;
-    parser.add("t", "test", :optionalArg, :hidden);
+    parser.add("test", :optionalArg, :hidden);
     with (parser.parse(["foo", "--test"])
         .case(Error: assert(false)))
     {
         assert(get("test") == "");
         assert(remaining == ["foo"]);
     }
-    with (parser.parse(["-t", "2"])
+    with (parser.parse(["--test", "2", "foo"])
         .case(Error: assert(false)))
     {
-        assert(get("test") == "2");
-        assert(remaining.empty);
+        assert(get("test") == "");
+        assert(remaining == ["2", "foo"]);
     }
     with (parser.parse(["--test=2", "foo"])
         .case(Error: assert(false)))
@@ -369,16 +369,14 @@ class GccArgParser : ArgParser
         (void | Error) parseArg(ArgInfo argInfo, string flagInfo) {
             if (argInfo.kind == :noArg || argInfo.kind == :optionalArg) {
                 result.foundArgs[argInfo.longOrShort] = null;
-                if (argInfo.kind == :noArg) return;
+                return;
             }
             if (args.empty) {
-                if (argInfo.kind == :optionalArg) return;
                 return new Error("Flag $flagInfo missing parameter");
             }
             auto parameter = args[0];
             args = args[1 .. $];
             if (parameter.startsWith("-")) {
-                if (argInfo.kind == :optionalArg) return;
                 return new Error("Flag $flagInfo missing parameter");
             }
             return parseArgParameter(argInfo, parameter, flagInfo);