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
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.
VideoCommon: Cache native vertex formats

We are used to have a 1:1 mapping of GX vertex formats and the native (OGL + D3D) ones, but there are by far more GX ones.
This new cache maps them directly so that we don't flush on GX vertex format changes as long as the native one doesn't change.

The idea is stolen from galop1n.
enum CPUState: rename CPU_* to STATE_*
CoreParameter: add enum CPUBackend
Don't install segfault handler in interpreter mode
Merge pull request #567 from degasus/master

ConfigManager: fix alignment
Merge pull request #463 from degasus/vertex_format_cache

VideoCommon: Cache native vertex formats
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