Naive cgo bindings for the C-API of hdf5.

http://go.pkgdoc.org/github.com/sbinet/go-hdf5/pkg/hdf5

• Hello world example: https://github.com/sbinet/go-hdf5/blob/master/cmd/test-go-hdf5/test-go-hdf5.go

• Writing/reading an hdf5 with compound data: https://github.com/sbinet/go-hdf5/blob/master/cmd/test-go-cpxcmpd/test-go-cpxcmpd.go

• Only version 1.8.x of HDF5 is supported.

• the h5pt packet table interface is broken.