Declare public methods

[JeffFessler]

Addresses #1216 by declaring public methods as such (those that are not exported and thuse require module scoping).

I used the union of the list of methods in the history file:
https://github.com/JuliaIO/HDF5.jl/blob/master/HISTORY.md#v014
and the methods mentioned in HDF5.jl

Any maintainer (or I) can edit the list in this PR to remove any names that should not be public.

This works only in Jula v0.11.0 and beyond. Currently, eval Expr is needed to avoid problems with code coverage in earlier versions. Eventually, when the long-term release is >= 0.11, then this code can be simplified to avoid eval Expr

I learned this Eval trick over at JuliaMath/FFTW.jl#329

[JeffFessler]

The first version passed all tests except the formatter.
So then I ran the formatter (which changed tons of files unrelated to my PR).
I committed only the change related to indentation in the lines changed in HDF5.jl by this PR.
Hopefully that will appease the formatter checker!

[mkitti]

Thank you!