Add --force_curly_braces option to insert braces around single-statem…

[burner]

…ent bodies.

When enabled, the preprocessor inserts synthetic { and } tokens around braceless bodies for all block header constructs: if, else, for, foreach, while, do, scope, synchronized, with, catch, debug, version, finally, and their combinations (static if, static foreach, etc.). Implementation uses token stream preprocessing so the formatter's existing brace-handling logic handles style and indentation naturally. Synthetic tokens use size_t.max-based indices to avoid collisions with AST info lookups. Handles compound constructs correctly:

• try/catch/finally chains as single statements
• Nested braceless blocks (each level gets its own braces)
• Mixed braced/braceless siblings (only braceless branches get braces)
• else if/else version/else static if chains (no double-wrapping)
• debug/version with and without parens
• Respects // dfmt off / // dfmt on regions

[WebFreak001]

I just edited the code locally to enable your flag by default (dfmt_force_curly_braces = OptionalBoolean.t) and then reran the tests and checked some outputs:

Some bugs I encountered:

void foo() {
	string command;
	version (Posix) command ~= " 2> /dev/null 1> /dev/null";

	version (Posix) command ~= " 2> /dev/null 1> /dev/null";

	unittest
	{
		version (Posix) command ~= " 2> /dev/null 1> /dev/null";
	}
}

results in weird whitespace - I would like if the empty line could be after the closing brace instead:

void foo()
{
    string command;
    version (Posix)
    {
        command ~= " 2> /dev/null 1> /dev/null";

    }
    version (Posix)
    {
        command ~= " 2> /dev/null 1> /dev/null";

    }
    unittest
    {
        version (Posix)
        {
            command ~= " 2> /dev/null 1> /dev/null";
        }
    }
}

---

and it would be nice if you could make comments work, but not a dealbreaker:

unittest
{
	if (imin.value > 0x10FFFFUL) // ??
		imin.value = 0x10FFFFUL; // ??
}

->

unittest
{
    if (imin.value > 0x10FFFFUL) // ??
    {
        imin.value = 0x10FFFFUL;
    } // ??
}

---

The whitespace here is a bit broken, but the braces are fine imo:

unittest
{
	version (Windows) __locale_decpoint = save;
	else version (Foo) __locale_decpoint = save;
	else debug __x = 3;
	else foobar();
}

->

unittest
{
    version (Windows)
    {
        __locale_decpoint = save;
    }
    else version (Foo)
    {
        __locale_decpoint = save;
    }
    else
    {
        debug
        {
            __x = 3;
        }
    else
        {
            foobar();
        }
    }
}

---

It doesn't support debug / else debug / else blocks yet:

void main() {
debug (Foo) foo();
else debug (Bar) bar();
else baz();
}

->

void main()
{
    debug (Foo)
    {
        foo();
    }
    else
    {
        debug (Bar)
        {
            bar();
        }
        else
        {
            baz();
        }
    }
}

---

Perhaps with (...) switch (...) blocks should not be nested since they are kind of a paradigm to write together, but I'm not particularly set on that idea:

unittest
{
	with (SomeEnum) final switch (value)
	{
	case a:
		aa();
		break;
	case b:
		bb();
		break;
	}
}

should stay and not get the {} for the with (SomeEnum)