stellarium: Moved require to exlibs.
Revert "stellarium: Moved require to exlibs."

This reverts commit 99aa33e9cbde6f4d01cbe0069b03b4326482c177.
Moved require to exlib.
Stellarium: Added pkg_preinst in exlib, removed src_install.
stellarium: ammended exlib.
All Packages: Made exlibs self-sustained.
xephem: Modified pkg_postinst.
xephem: Modified exlib.
Revert "xephem: Modified exlib."

This reverts commit ba34ab0e6e49ebd5ced126756d54580d9f8a4552.
Revert "Revert "xephem: Modified exlib.""

This reverts commit 402e1488bcbe7ca1302922456f7c9c50e23c6457.
xephem: Not export pkg_postinst.
Revert "xephem: Not export pkg_postinst."

This reverts commit 9aa9169ab77fcb5485f3584e77b6e526c46b6873.