Description of problem:
texdoc can't locate documentation files after installation of tetex-doc.
The tetex-doc subpackage doesn't hash the tex files after
being installed (or uninstalled).

Version-Release number of selected component (if applicable):
tetex-3.0-4

Steps to Reproduce:
1. tetex-doc isn't installed by default (at least in some FC installation
   profiles)
2. install tetex-doc manually
3. try to view some doc file. Example:
   texdoc listings
4. nothing happens


Additional info:
Solution: also add the %post and %preun scripts to the tetex-doc subpackage.

%post doc
[ -x %{_bindir}/texhash ] && /usr/bin/env - %{_bindir}/texhash 2> /dev/null
exit 0

%postun doc
[ -x %{_bindir}/texhash ] && /usr/bin/env - %{_bindir}/texhash 2> /dev/null
exit 0