compiler: varargs slices do not escape in runtime

Also, don't try to allocate an empty slice on the stack, as it will
confuse the GCC backend.

Also add a few trivial style, code formatting, and debug output fixes.

Updates golang/go#17431

Change-Id: I6dfe34b0553f377e4f92ede934dcfa6222fe9dad
Reviewed-on: https://go-review.googlesource.com/40983
Reviewed-by: Than McIntosh <thanm@google.com>
1 file changed