Compute and display SPF execution statistics

Detailed SPF statistics, all around time spent executing various pieces of SPF
such as the SPF algorithm itself, installing routes, pruning unreachable networks
etc.

Reason codes for firing up SPF are:
R - Router LSA, N - Network LSA, S - Summary LSA, ABR - ABR status change,
ASBR - ASBR Status Change, AS - ASBR Summary, M - MaxAge

Signed-off-by: Dinesh G Dutt <ddutt@cumulusnetworks.com>
Reviewed-by: JR Rivers <jrrivers@cumulusnetworks.com>
Reviewed-by: Scott Feldman <sfeldma@cumulusnetworks.com>
Reviewed-by: Ayan Banerjee <ayan@cumulusnetworks.com>
Reviewed-by: Paul Jakma <paul@opensourcerouting.org>
11 files changed