libgo: keep c0 and c1 out of runtime.inc

    
    The constants named c0 and c1 turn up as macros in runtime.inc.  This
    reportedly breaks building on Solaris 11, where there is a system struct
    that has a field named c1.  The constants aren't needed by the runtime C
    code, so avoid the problem by grepping them out.
    
    Reviewed-on: https://go-review.googlesource.com/31730

From-SVN: r241432