(RGUI) Host menu_type_is out of rgui.c and into menu_settings.c
fix variable shadowing in command.c
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.
(RGUI) Combine resolve_names functions into one
(RGUI) history_parse and directory_parse become one function
(RGUI) Combine menu_parse and menu_resolve_names
Move more logic to menu_parse_and_resolve - rgui.c and rmenu.c
should become purely rasterizers only
(RGUI) menu_set_settings_populate_entries moved to menu_common.c and
renamed menu_populate_entries
(frontend) Add some workarounds for Emscripten
(frontend) Add more code that should allow for Emscripten support
in frontend.c
Merge pull request #378 from lioncash/struct-optimizing-crap

Optimize some struct sizes and stuff.
Move initing/deiniting of menu_list over to menu_common.c - turn
rgui.c into a rasterizer
(RGUI) Integrate rguidisp.c into rgui.c
(RGUI) Move toggle_settings code to menu_settings.c
(RGUI) Style nits
(RGUI) Turns rgui.c into a raster driver for common
menu code - rmenu.c and rmenu_xui.cpp will need to be
adapted accordingly
Move popping of RGUI list out of rgui.c rasterizer - should make
all of the RGUI list state code self-contained inside menu_common.h
(GX) Build fixes
[Android] Add rewinding granularity to the general settings.