Delegating bind statements

The following example outlines a problem that can arise when generic instantiations cross multiple different modules:

# module A
proc genericA*[T](x: T) =
  mixin init
  init(x)

import C
# module B
proc genericB*[T](x: T) =
  # Without the `bind init` statement C's init proc is
  # not available when `genericB` is instantiated:
  bind init
  genericA(x)

# module C
type O = object
proc init*(x: var O) = discard

# module main
import B, C
genericB O()

In module B has an init proc from module C in its scope that is not taken into account when genericB is instantiated which leads to the instantiation of genericA. The solution is to forward these symbols by a bind statement inside genericB.