Make include-what-you-use happy with files in source/network and
fix what needs to be fixed.
Ref: #8086
Signed-off-by: Ralph Sennhauser <ralph.sennhauser@gmail.com>
The user doesn't have to fiddle with `std::shared_ptr`.
And two (more unrelated) things: use `std::unordered_map`, use a
`std::find_if` in the callback.
Comments By: @vladislavbelov, @Stan
Differential Revision: https://code.wildfiregames.com/D5239
This was SVN commit r28048.
