cmd/gc: steal escape analysis info when inlining

Usually, there is no esc info when inlining, but there will be when generating inlined wrapper functions.

If we don't use this information, we get invalid addresses on the stack.

Fixes issue 5056.

R=golang-dev, rsc
CC=golang-dev, remyoudompheng
https://codereview.appspot.com/7850045