HDF5 doesn't have a single type that this defines to anymore (from 1.12
at least), so the forward declaration isn't possible without
introspecting which version of HDF5 is being used. Just use HDF5's
headers and be done with it.

Fix the installed header search path.

See merge request !1

This prevents ParaView from packaging properly.

The `XDMF_EXPORTS` symbol was not getting defined correctly since it was
being set on the wrong target. This was causing windows builds to
failed. Fixed that.

warnings: avoid string + int and use stringstream instead

See merge request !51

Fix shadowing warnings

See merge request !54

XdmfGridTemplate: use boolean && rather than bitwise &

See merge request xdmf/xdmf!53

The code was useless before since it declared a variable that
immediately left the scope.

These instances are best fixed by renaming or removing the (unused)
shadowing declaration.

Fix warnings

See merge request xdmf/xdmf!52

Since it is inherited, the destructor needs to be virtual to release
memory properly.

XdmfGridController: add missing `return` statement

See merge request xdmf/xdmf!50

replace atoi for seek because that can get overflow easily

See merge request xdmf/xdmf!49

With this we at least get full unsigned int range and a warning
if we overflow.

Cmake cleanup

See merge request xdmf/xdmf!39

Set them at the top-level instead.

These were all overwriting each other otherwise.