Some flags are defined during statistics generation and output. They use
the prefix STAT_* which is also used for other purposes. Rename them
with the new prefix STAT_F_* to differentiate them from the other
usages.
This commit is the first one of a serie which adjust naming convention
for stats module. The objective is to remove ambiguity and better
reflect how stats are implemented, especially since the introduction of
stats module.
This patch renames elements related to proxies statistics. One of the
main change is to rename ST_F_* statistics indexes prefix with the new
name ST_I_PX_*. This remove the reference to field which represents
another concept in the stats module. In the same vein, global
stat_fields variable is renamed metrics_px.
Extract functions related to HTML stats webpage from stats.c into a new
module named stats-html. This allows to reduce stats.c to roughly half
of its original size.
