Expose more SRAM settings in RGUI.

Also treat save state slot -1 as the "auto save slot".
(PSP) Add default binds
(PSP) Add some missing defines
(PSP) Flesh out psp_input_set_keybinds
(PSP) Check if input and input_data points to something in
graphics init function
(PSP) Implement autodetect_enable
(PSP) Fix default joykey binds
(PSP) Set optimization to -O2 - -O3 is unsafe on my
PSP GCC toolchain
Add detection of more SIMD instruction sets.
(PSP) Hook up RGUI toggle to 'Note' button
(PSP) (Menu common) Add file paths
(PSP) Add RETRO_SIMD_VFPU
(PSP) improved screen blitting, using a fullscreen sprite instead of a
sceGuCopyImage.
Merge pull request #552 from aliaspider/master

(PSP) improved screen blitting, using a fullscreen sprite instead of a
(PSP) added RGB to BGR color conversion in psp_frame
Merge pull request #553 from aliaspider/master

(PSP) added RGB to BGR color conversion in psp_frame
(PSP) Refactor init_texture
(PSP) Refactor init_texture / dehardcode pointer addresses
(PSP) Style nits
(PSP) Start implementing poke interface