Convert all includes to relative paths.
Fix Linux build
Dolphin now builds on Linux with only Source/Core as include dir
Scope the Windows include directory to only point to Source/Core/.

Also fix the Windows build with this change.
Fix the OSX build.

Turns out Dolphin uses some macros that clash on OSX. However thankfully, this include is only used in Frame.cpp.
Add an automated tool that does basic checking of includes sort order.
Fix more header sorting issues in Common/ (now check-includes clean).
Fix more header sorting issues in DiscIO/ (now check-includes clean).
Fix more header sorting issues in AudioCommon/ (now check-includes clean).
Fix more header sorting issues in InputCommon/ (now check-includes clean).
Fix more header sorting issues in VideoCommon/ (now check-includes clean).
Fix more header sorting issues in DolphinWX/ (now check-includes clean).
Fix more header sorting issues in VideoBackends/ (now check-includes clean).
Fix LinearDiskCache.h relying on a file not directly included.
Fix more header sorting issues in Core/ (now check-includes clean).
Fix the Windows build in relation to the recent changes.
Forgot to move DSPTool over. Fixed now.
Fix the Android build.

Required the removal of EGL.h from EGL.cpp.

Removed the similar includes from AGL.cpp, GLX.cpp, and WGL.cpp to retain consistency.
All GL interfaces are now centralized on GLInterface.h
Fix the Windows build for the final time.
Merge pull request #88 from lioncash/relative-includes

Relative includes