Added system definition for Foundry devices:
 - BigIron 4000 sysoid: .1.3.6.1.4.1.1991.1.3.6.2
 - BigIron 8000 sysoid: .1.3.6.1.4.1.1991.1.3.7.2
 - BigIron RX sysoid:   .1.3.6.1.4.1.1991.1.3.40.2.2

Patch sign off: dominik.klein@googlemail.com
Formatted foundry.xml with 2 space indentation