Ignore generated string.h
Sane programmers do not pass NULL to deinit
Redefine ws_object_deinit

The function now invokes all the deinitialization callbacks for a type.
Also, it doesn't return anything anymore, since the information is
useless.
Fix tests for ws_object
Fix tests for ws_set
Merge pull request #374 from neithernut/add-commands-missing_gitignore_entry

Ignore generated string.h
Merge pull request #377 from neithernut/mod-objects-deinit

Redefine ws_object_deinit
Add UseLATEX module by Kenneth Moreland (kmorel)

This commit adds the UseLATEX module from https://github.com/kmorel/UseLATEX.
This is unproblematic regarding licensing, since the LGPL only applies
to code --and only to files containing the licensing header.
As the entire CMake setup isn't covered by the LGPL and the UseLATEX
module is made  part of that setup by this commit, no licensing issues
arise.
Do not build info pages
Use a seperate tex file for the manpage