This permits inlining functions with for loops and some switches, as
    they are lowered to if and goto statements before exporting them.
    
    This by itself only adds three new inlinable functions in the standard
    library: sort.Search, context.(*emptyCtx).String, and
    cmd/go/internal/work.(*Builder).disableBuildID.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/181197

From-SVN: r272131