This reverts commit 98f2682f.

For the moment, new API functions are introduced. If existing API
functions are called, the why3server is not used.

* why3config.ml
(plugins_auto) if plug-ins dir is absent, do not attempt to add plug-ins

Yannick Moy authored Sep 22, 2014 and Johannes Kanig committed Mar 17, 2016

Function Sysutil.relativize_filename does not work well when its first
argument contains special subpaths for the parent and current directories
(".." and "."). Provide a function Sysutil.normalize_filename that removes
such subpaths, to be called before Sysutil.relativize_filename.

Drivers that parse the cpulimit output expect a line of the form
"why3cpulimit time : XXX s" for the total cpu time of the prover run.

The Win version of cpulimit prints an additional line
"why3cpulimit real time : XXX s" for the wall-clock time.
This line is ignored by drivers, since we use the cpu time
and not the real time to establish time limits.

also, drop command-line tags %T and %U which were only used
with why3cpulimit and never as an actual prover parameter.