cmd/cgo: extend implementation comment
This is the plan for how to make host linking work with
the rest of the system.
There are two complications:
1. It is a goal to preserve the property that pure Go programs
(even ones importing "net") can be compiled without needing
gcc, so that a Go toolchain download works out of the box.
This forces the support for two linking modes: with and without
gcc.
2. It is a goal to allow users with old copies of SWIG to continue
to use those copies. This forces the support for "internal only"
packages. Perhaps it is reasonable to require a new SWIG.
I don't know.
R=iant
CC=golang-dev
https://golang.org/cl/
7433043