// The printer is not good enough at printing comments in the
	// right place when we start editing the AST behind its back,
	// so we use ast1 to look for the doc comments on import "C"
	// and on exported functions, and we use ast2 for translating
	// and reprinting.
	// In cgo mode, we ignore ast2 and just apply edits directly
	// the text behind ast1. In godefs mode we modify and print ast2.