compiler, runtime: harmonize types referenced by both C and Go

compiler, runtime: harmonize types referenced by both C and Go

    Compiling with LTO revealed a number of cases in the runtime and
    standard library where C and Go disagreed about the type of an object or
    function (or where Go and code generated by the compiler disagreed). In
    all cases the underlying representation was the same (e.g., uintptr vs.
    void*), so this wasn't causing actual problems, but it did result in a
    number of annoying warnings when compiling with LTO.

    Reviewed-on: https://go-review.googlesource.com/c/160700

From-SVN: r268923