create generic gl::buffer, rebase gl::ubo onto it

gl/buffer.h

@@ -0,0 +1,44 @@
+#pragma once
+
+#include "object.h"
+#include "bindable.h"
+
+namespace gl
+{
+    class buffer : public object
+    {
+        static GLuint binding_points[13];
+
+    public:
+        enum targets
+        {
+            ARRAY_BUFFER = 0,
+            ATOMIC_COUNTER_BUFFER,
+            COPY_READ_BUFFER,
+            COPY_WRITE_BUFFER,
+            DISPATCH_INDIRECT_BUFFER,
+            DRAW_INDIRECT_BUFFER,
+            ELEMENT_ARRAY_BUFFER,
+            PIXEL_PACK_BUFFER,
+            PIXEL_UNPACK_BUFFER,
+            SHADER_STORAGE_BUFFER,
+            TEXTURE_BUFFER,
+            TRANSFORM_FEEDBACK_BUFFER,
+            UNIFORM_BUFFER
+        };
+
+    private:
+        static GLenum glenum_target(targets target);
+
+    public:
+        buffer();
+        ~buffer();
+
+        void bind(targets target);
+        void bind_base(targets target, GLuint index);
+        static void unbind(targets target);
+
+        void allocate(targets target, int size, GLenum hint);
+        void upload(targets target, const void *data, int offset, int size);
+    };
+}