Log Message:
Initial import of tex-xkeyval, version 2.5f:

This package is an extension of the keyval package and offers additional
macros for setting keys and declaring and setting class or package options.
The package allows the programmer to specify a prefix to the name of the
macros it defines for keys, and to define families of key definitions;
these all help use in documents where several packages define their own
sets of keys.