cmd/5g, cmd/6g, cmd/8g: provide embedded trampolines with argument size information
An embedded trampoline is a function that exists to marshal
a receiver of type *S to a receiver of type *T when T is an
embedded field in S.
Embedded trampolines are generated by a special path through
the compiler and are not subject to the general analysis and
annotation done to functions. Their effects must be provided
explicitly.
R=golang-dev, r, daniel.morsing, minux.ma
CC=golang-dev
https://golang.org/cl/
9874043