Examples:
- "foo$1" becomes "pkg.foo$1"
- "init$1" (meaning the first declared "init" function) becomes "init#1",
to distinguish it from "init$1" (meaning the first anonymous function
within the synthetic "init" function that initializes package-level vars).
It is now an invariant that all source-level (non-synthetic)
functions have distinct names, and that all names include the
enclosing package. Added test for this.
+ updated various clients.
LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/122750043
4228ee8063