Revert "Improve FreeBSD support (install pkgconfig files to libdata dir in FreeBSD)"

This reverts commit 8c79fd92270a85f1f2e599e6ec90b10eb855b0b3.

Those things should be handled by FreeBSD ports system as they are currently.
Description how to handle those thing manually are written at LXDE Wiki site, see
http://wiki.lxde.org/en/LXDE:PCManFM_build_and_setup_guide#Compile_and_Install_-_FreeBSD