add comments to packed pixel format enums to clarify bit order

src/common/pixelformat.h

@@ -51,11 +51,11 @@ enum PixelFormat
 	PIXELFORMAT_LA8, // Same as RG8, but accessed as (L, L, L, A)
 
 	// packed formats
-	PIXELFORMAT_RGBA4,
-	PIXELFORMAT_RGB5A1,
-	PIXELFORMAT_RGB565,
-	PIXELFORMAT_RGB10A2,
-	PIXELFORMAT_RG11B10F,
+	PIXELFORMAT_RGBA4,    // LSB->MSB: [a, b, g, r]
+	PIXELFORMAT_RGB5A1,   // LSB->MSB: [a, b, g, r]
+	PIXELFORMAT_RGB565,   // LSB->MSB: [b, g, r]
+	PIXELFORMAT_RGB10A2,  // LSB->MSB: [r, g, b, a]
+	PIXELFORMAT_RG11B10F, // LSB->MSB: [r, g, b]
 
 	// depth/stencil formats
 	PIXELFORMAT_STENCIL8,