LibGL: Implement glDepthFunc

Author: https://github.com/sunverwerth
Commit: 5b9c87a8b5
Pull-request: https://github.com/SerenityOS/serenity/pull/9451
Reviewed-by: https://github.com/Quaker762 ✅
Reviewed-by: https://github.com/alimpfard

Userland/Libraries/LibGL/SoftwareGLContext.h

@@ -85,6 +85,7 @@ public:
     virtual void gl_get_booleanv(GLenum pname, GLboolean* data) override;
     virtual void gl_get_integerv(GLenum pname, GLint* data) override;
     virtual void gl_depth_range(GLdouble min, GLdouble max) override;
+    virtual void gl_depth_func(GLenum func) override;
     virtual void present() override;
 
 private: