Created KMS mode (markdown)

KMS-mode.md

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+## Purpose
+KMS (Kernel Mode Setting) mode is a feature where RetroArch can use the OpenGL driver outside Xorg, running straight in the virtual terminal. It is a fairly obscure feature, but very powerful in a console scenario.
+
+## Requirements
+To use KMS mode you need:
+
+- Recent version of MESA (9.0+)
+- libgbm 9.0+, libdrm
+- Open source driver which supports KMS
+
+These require a fairly up-to-date distro.
+After compiling RetroArch, you should see this when running `retroarch --features`:
+
+	KMS:
+		KMS/EGL context support: yes
+
+If KMS mode is working correctly, RetroArch should start up outside Xorg as well.