wpa_supplicant: Add option -I for additional config file

This option can be used only for global parameters that is not going
to be changed from settings.

Change-Id: I4f18aa0a8503cf8cc3a847ac9fcc15419291edf0
Signed-off-by: Dmitry Shmidt <dimitrysh@google.com>
Signed-off-by: Iliyan Malchev <malchev@google.com>
10 files changed