Correctly indent the body of functions that have been declared
over multiple lines. See http://play.golang.org/p/MHMwNDbFyf for
an example.

Previously, the body of the function would be indented as deep as
the continuation line of the function declaration. Now it gets
indented as deep as the func keyword.

R=adonovan, cw, patrick.allen.higgins
CC=golang-dev
https://golang.org/cl/7628043