[SETUP:REACTOS] Adapt the 1st-stage GUI setup to compile with the setuplib.

[SETUP:REACTOS] Adapt the 1st-stage GUI setup to compile with the setuplib.

svn path=/branches/setup_improvements/; revision=75544

[SETUP:REACTOS] More interfacing of the 1st-stage GUI installer with the setuplib.

- Add a ConvertNtPathToWin32Path() helper function that allows converting
  NT paths like: \Device\CdRom0\i386\txtsetup.sif file into a Win32 path
  that the Win32 versions of the SetupApi functions (e.g. SetupOpenInfFileW)
  can accept.
  Note that RtlNtPathNameToDosPathName() cannot be used here because this
  function only works for NT paths within the \DosDevices\ (or \??\) NTObj
  directory, and not in other directories.

- Use this helper function in the implementation of SetupOpenInfFileExW.
  Now the txtsetup.sif function can be loaded by setuplib *when being used*
  by the 1st-stage GUI installer!

- Remove deprecated code.

svn path=/branches/setup_improvements/; revision=75668
svn path=/branches/setup_improvements/; revision=75721
svn path=/branches/setup_improvements/; revision=75750