Due to an include conflict between /usr/include/poll.h and
maxscale/server/include/poll.h the latter was moved to
maxscale/server/include/maxscale/poll.h.
Once 1.4 is out, all maxscale header files will be moved to that
same sub-directory. That will prevent include conflicts and also
make it easy to see which include files belong to maxscale and
which do not.
The polling statistics collection used atomic_add to increment values. This
is not an optimal way to update statistical values. Moved to per thread
values which are summed up when they are read.
Moved the functions used to gather polling statistics to their own file and
created a specific data type for statistics.
