This fixes a mysterious, long-standing crash that's been bothering me on
ipod6g for ages: a silent stack overflow in the sound mixing thread (which
is triggered upon loading a new sound, apparently) will thrash the memory
which is located directly before it in the address space.
In this case, it was the SDL_ButtonState variable which stores the mouse
button state that was being trashed. This was manifesting itself by making
the player always run forward, since MOUSE2 is mapped to +forward by
default.
Fix this by quadrupling the stack size of SDL-spawned threads (not the main
thread) from 1 KB to 4 KB.
Change-Id: I2d7901b7cee1e3ceb1ccdebb38d4ac5b7ea730e1
d1a92aafff