The D3D backend was always forcing Anisotropic filtering when that is enabled regardless of how the game chose to configure the texture filtering registers; this causes the same issues as "Force Filtering" without Anisotropy, such as causing game UI elements to no longer line up adjacent correctly. Historically, OpenGL's Anisotropy support has always worked "better" than D3D's due to seeming to not have this problem; unfortunately, OpenGL's Anisotropy specification only gives GL_LINEAR based filtering modes defined behavior, with only the mipmap setting being required to be considered. Some OpenGL implementations were implicitly disabling Anisotropy when the min/mag filters were set to GL_NEAREST, but this behavior is not required by the spec so cannot be relied on.

This reverts commit e2a1a085b6a9f36b23128872de85da727d231882, reversing
changes made to 2aea549eef85ba165672c8355d0e90781d805efd.

VideoConfig: Replace FastDepthCalc by ForcedSlowDepth.

Fast depth is now more accurate than slow depth and should always be used.
The option will be kept in a different form as it is still used as a hack to fix some games.
Also, the slow depth code path will still be relied upon by cards that don't support GL_ARB_clip_control.

And rename it to VideoBackendBase because of conflicts within the backends itself.

Use ffmpeg for Windows Video Dumping instead of VFW

They share the same format, so there is no need to separate their configs.

Also gets rid of global headers