Generator improvements

[RolandTaverner]

1. out/windows/win32/system/diagnostics/debug => out/windows/win32/system/diagnostics/debug_
2. NativeEncodingAttribute - generate comment // Native encoding: ansi
3. NativeBitfieldAttribute - generate comment like // Native bit field: Format: [0-3], Reserved1: [4-6], Msf: [7]
4. Make bitfield field names unique in one structure instead of globally, so in the future they will not be renamed all at once

At least this works

import windows.win32.ui.windowsandmessaging;
int main(string[] args)
{
	wstring c = "Caption";
	wstring msg = "Hello!";
	MessageBoxW(HWND(null), PWSTR(cast(wchar*)msg.ptr), PWSTR(cast(wchar*)c.ptr), 0);
	return 0;
}