AVIDump: cleanup
AVIDump: update ffmpeg/libav API usage

libav 10 was released on May 10th, 2014 and it drops support for some
long-deprecated stuff like avcodec_encode_video().
CMake: remove unused/duplicate definitions
CMake: mention ffmpeg in libav messages

We support both.
CMake: update min. libav/ffmpeg library versions
AVIDump: rename frame variables
Fix patches not being loaded when running real gc bios.
Changed lingering header include guards to pragma once.

Some headers where using #ifndef to guard being including multiple times. But most were using pragma once. So for consistency I changed them all to use pragma once.
[Core] Clean up the DSP disassembler

- Get rid of deletes.
- Clean out all of the sprintf calls. Now std::string based.
- Fully explicit function names, etc.
enum CPUState: rename CPU_* to STATE_*
CoreParameter: add enum CPUBackend
Don't install segfault handler in interpreter mode
Merge pull request #546 from workhorsy/header_guard_to_pragma_once

Changed lingering header include guards to pragma once.
Merge pull request #547 from lioncash/cleanups

Clean up the DSP disassembler a little.
Merge pull request #328 from Tilka/enum_cpubackend

Don't add segfault handler in interpreter mode
Merge pull request #362 from Tilka/ffmpeg_libav_new

AVIDump: use new ffmpeg/libav API
VideoCommon: Get rid of an snprintf call in VideoConfig.cpp
Merge pull request #571 from lioncash/snprintf

VideoCommon: Get rid of an snprintf call in VideoConfig.cpp
Introduce the revised coding style.
Merge pull request #410 from lioncash/coding-style

Introduce the revised coding style.