compiler: show readable names in escape analysis messages

Call message_name when printing a variable for an escape analysis
message.  This implies changing the AST dumps, which is fine.

Change-Id: Ief479a4795ab1f3ca697da365a4266e70745fb0a
Reviewed-on: https://go-review.googlesource.com/90296
Reviewed-by: Cherry Zhang <cherryyz@google.com>
3 files changed