libcap is a library for getting and setting POSIX.1e 
(formerly POSIX 6) draft 15 capabilities.

More information (POSIX 1e and 2c drafts):  
http://wt.xpilot.org/publications/posix.1e/download.html

Usage tutorial (Olaf Kirch: Using Capabilities - 2002): 
http://www.lst.de/~okir/blackhats/node125.html 

Active development of libcap v2 is in filesystem capabilities, see:
http://www.kernel.org/pub/linux/libs/security/linux-privs/README

And maybe read Serge E. Hallyn' article
POSIX file capabilities: Parceling the power of root
http://www.ibm.com/developerworks/linux/library/l-posixcap.html?ca=dgr-lnxw06LinuxPOSIX

If you uninstall this package, you will need to manually remove the
/usr/include/sys/capability.h header.