(Android) Use the same log tag ("RetroArch") for all events

This allows filtering using logcat (e.g.: adb logcat RetroArch:V *:S),
which should be more efficient than grep.
Document some input-related variables
Delete duplicate MSVC solution
.gitignore
Fix/reimplement input flushing

This fixes:

- menu toggle erratically not working on Android
- stray input going to libretro core when resuming content
- bound keys triggering as soon as they're bound on Android
- menu key repeat also repeating keys which should not be repeated
- issues caused by relying on timeouts for flushing

Architectural changes:

- menu_ctx_driver_t::input_postprocess now takes state and old_state
  (this allows getting rid of menu_handle_t::trigger_state)

Related changes:

- remove some no-op input_postprocess handlers (same effect as NULL)
- menu_iterate now uses the parameters passed to it, instead of
  polling menu_input
- menu_input is now merged into meta_input_keys_pressed
Merge pull request #1064 from CyberShadow/pull-20140928-032517

Fix/reimplement input flushing