Comment the byte slice conversion

unsafe.go

@@ -11,5 +11,15 @@ func unsafeIndex(base unsafe.Pointer, offset uintptr, elemsz uintptr, n int) uns
 }
 
 func unsafeByteSlice(base unsafe.Pointer, offset uintptr, i, j int) []byte {
+	// See: https://github.com/golang/go/wiki/cgo#turning-c-arrays-into-go-slices
+	// 
+	// This memory is not allocated from C, but it is unmanaged by Go's
+	// garbage collector and should behave similarly, and the compiler
+	// should produce similar code.  Note that this conversion allows a
+	// subslice to begin after the base address, with an optional offset,
+	// while the URL above does not cover this case and only slices from
+	// index 0.  However, the wiki never says that the address must be to
+	// the beginning of a C allocation (or even that malloc was used at
+	// all), so this is believed to be correct.
 	return (*[maxAllocSize]byte)(unsafeAdd(base, offset))[i:j:j]
 }