Optimize some struct sizes.

This is the list of reduced sizes:

file: dsound.c         - struct dsound_t reduced from 56 bytes to 52 bytes.
file: shader_parse.h   - struct gfx_fbo_scale reduced from 32 bytes to 28 bytes.
file: thread_wrapper.c - struct texture reduced from 28 bytes to 24 bytes.
file: libretro.h       - struct retro_hw_render_callback reduced from 40 bytes to 36 bytes.
file: movie.c          - struct bsv_movie reduced from 36 bytes to 32 bytes.
file: netplay.c        - struct delta_frame reduced from 16 bytes to 12 bytes.
file: performance.h    - struct rarch_perf_counter_t reduced from 40 bytes to 32 bytes.
Shrink another struct. This shrinks audio_lock from 32 bytes to 24 bytes.
Merge pull request #378 from lioncash/struct-optimizing-crap

Optimize some struct sizes and stuff.