pmdacifs: Initial PMDA Code

Inital CIFS PMDA code using the stats given in procfs (DSO and Daemon),
using previously reserved domain 121.

Exports statistics from the /proc/fs/cifs/Stats file. In this initial
version we make use of the stats given globally for the cifs module
along with data provided per each mounted cifs share.

Requires at least the cifs kernel module to be loaded in order to
give the global cifs metrics and with each mounted cifs share comes
it's own instance of metrics.

QA is given with qa/656 which runs the pmda in DSO mode with a fake
root given (borrowed from xfs pmda getenv()) to provide testing data
instead of needed mounted cifs shares on the qa host. Also running
with valgrind during the test.

Code checked with coverity and has no reported issues.