Add new paths for the OUI file and factorize the code to find it.

 * Add two new paths for searching the OUI file:
   /var/lib/ieee-data/oui.txt /usr/share/ieee-data/oui.txt
   On Debian, aircrack-ng relies on the package ieee-data to get
   the OUI data. This package now uses the above two paths.

 * Add also "/var/lib/misc/oui.txt" that was removed on r2278.

 * Sync the path defines both on src/airodump-ng.h and
   scripts/airdrop-ng/airdrop/libOuiParse.py

 * Factorize and simplify the logic to find the OUI file.



git-svn-id: http://svn.aircrack-ng.org/trunk@2455 28c6078b-6c39-48e3-add9-af49d547ecab