This header doesn't actually make use of MathUtil.h within itself, so
this can be removed. Many other source files used VideoCommon.h as an
indirect include to include MathUtil.h, so these includes can also be
adjusted.
While we're at it, we can also migrate valid inclusions of VideoCommon.h
into cpp files where it can feasibly be done to minimize propagating it
via other headers.
Also ensure that all members of the class are initialized on
construction as well. Previously the bool indicating if options are
dirty wouldn't be initialized, which could be read uninitialized if an
instance was constructed and then IsDirty() is called.
This catches most instances of configuration failures that can happen in a post processing shader.
Gives a user a helpful error message that lets them know what they have failed to set up correctly
This class loads all the common PP shader configuration options and passes those options through to a inherited class that OpenGL or D3D will have.
Makes it so all the common code for PP shaders is in VideoCommon instead of duplicating the code across each backend.
