PSP c souce files misses #ifdef PSP_FOOBAR

Hi,

in general one can add all c files to projects and SDL only picks the
parts that are reasonable for the arch depending on the config.h - in
case of the psp port, the guards are missing that make this possible.

at least the following subsystems are lacking the #ifdefs
audio
joystick
main
threads
timer
video

also the psp video header uses something from the pandora. I don’t have
a psp to test changes on - that’s the reason why there is no patch
attached here.

greetings
Martin