demos/flatwav: Post-SVN tidy

- Move source code from `trunk` into root directory.
- Update build files.

data/Tupfile.lua

@@ -595,7 +595,7 @@ tup.append_table(extra_files, {
  {"HD_Load/USB_boot_old/", VAR_PROGS .. "/hd_load/usb_boot_old/MeOSload.com"},
  {"HD_Load/USB_boot_old/", VAR_PROGS .. "/hd_load/usb_boot_old/enable.exe"},
  {"kolibrios/3D/3dsheart", VAR_PROGS .. "/demos/3dsheart/3dsheart"},
- {"kolibrios/3D/flatwav", VAR_PROGS .. "/demos/flatwav/trunk/flatwav"},
+ {"kolibrios/3D/flatwav", VAR_PROGS .. "/demos/flatwav/flatwav"},
  {"kolibrios/3D/mos3de", VAR_PROGS .. "/demos/mos3de/mos3de"},
  {"kolibrios/3D/info3ds/INFO3DS", VAR_PROGS .. "/develop/info3ds/info3ds"},
  {"kolibrios/3D/textures1", VAR_PROGS .. "/develop/libraries/TinyGL/asm_fork/examples/textures1"},