[ARB] Draw Buffers Blend

http://www.opengl.org/registry/specs/ARB/draw_buffers_blend.txt

C: void BlendEquationiARB(uint buf, enum mode);
New: void BlendEquationiARB(uint buf, BlendEquationMode mode);

C: void BlendEquationSeparateiARB(uint buf, enum modeRGB, enum modeAlpha);
New: void BlendEquationSeparateiARB(uint buf, BlendEquationMode modeRGB, BlendEquationMode modeAlpha);

C: void BlendFunciARB(uint buf, enum src, enum dst);
New: void BlendFunciARB(uint buf, BlendingFactorSrc src, BlendingFactorDest dst);

C: void BlendFuncSeparateiARB(uint buf, enum srcRGB, enum dstRGB, enum srcAlpha, enum dstAlpha);
New: void BlendFuncSeparateiARB(uint buf, BlendingFactorSrc srcRGB, BlendingFactorDest dstRGB, BlendingFactorSrc srcAlpha, BlendingFactorDest dstAlpha);