buildroot

sdl: needs tslib to be compiled first when selected.

If SDL is built before tslib, then SDL can't detect it at configure
time and so touchscreen's support in SDL is crappy.

Signed-off-by: Julien Boibessot <julien.boibessot@armadeus.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>