Add libaio and xfsdump utility (requirements for xfstests)

[thomas]

libaio (asynchronous I/O library) is needed to compile xfstests,
and xfsdump is called pretty frequently in the tests.

Snippets from the manpages:

The libaio library defines a new set of I/O operations which can
significantly reduce the time an application spends waiting at I/O.
The new functions allow a program to initiate one or more I/O
operations and then immediately resume normal work while the I/O
operations are executed in parallel.

xfsdump backs up files and their attributes in a filesystem. The
files are dumped to storage media, a regular file, or standard
output. Options allow the operator to have all files dumped, just
files that have changed since a previous dump, or just files
contained in a list of pathnames.

[pmenzel]

Next time, it’d be great, if you put each program addition in a separate commit (but the same branch).