compiler: support inlining functions that use index expressions

compiler: support inlining functions that use index expressions

    Also move the determine_types pass on an inlined function body to one
    place, rather than doing it ad hoc as needed.

    This adds 79 new inlinable functions in the standard library, such as
    bytes.HasPrefix and bytes.LastIndexByte.

    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/181261

From-SVN: r272133