LibGL+LibSoftGPU: Implement texture coordinate generation

Texture coordinate generation is the concept of automatically
generating vertex texture coordinates instead of using the provided
coordinates (i.e. `glTexCoord`).

This commit implements support for:

* The `GL_TEXTURE_GEN_Q/R/S/T` capabilities
* The `GL_OBJECT_LINEAR`, `GL_EYE_LINEAR`, `GL_SPHERE_MAP`,
  `GL_REFLECTION_MAP` and `GL_NORMAL_MAP` modes
* Object and eye plane coefficients (write-only at the moment)

This changeset allows Tux Racer to render its terrain :^)

Userland/Libraries/LibSoftGPU/Enums.h

@@ -68,4 +68,21 @@ enum class PrimitiveType {
     Quads,
 };
 
+enum TexCoordGenerationCoordinate {
+    None = 0x0,
+    S = 0x1,
+    T = 0x2,
+    R = 0x4,
+    Q = 0x8,
+    All = 0xF,
+};
+
+enum class TexCoordGenerationMode {
+    ObjectLinear,
+    EyeLinear,
+    SphereMap,
+    ReflectionMap,
+    NormalMap,
+};
+
 }