Reset vsl_log.wid in VSL_Setup.

This ensures that background threads like expire and ban lurker logs
using ID 0.
Fix memory leak on multiple -n / -N options
Add a VSLQ_Name2Grouping function to parse -g arguments
Add vut.[ch] to hold functions common to the utilities.

Move some parsing of options to these files.
Add VSL_Write* functions for writing binary log output.
Fix up the binary file reading VSL cursor
Enable binary file reading and writing in varnishlog
Add a VUT_Main implementation that all the VSL utilities should be
able to use.

Moved most functionality from varnishlog to VUT.
Document the varnish API options in a single place, using preprocessor
tables.

Enhance the usage() output of varnishlog using the new tables.

Add API utility header to extract data from the option headers.
Make the option documentation be generated from the option tables.
Add a lib/libvarnishtools library to hold common files for the tools.

Move vut.c and opt2rst.c there.
Let the synopsis be generated from the option table files
Add -P (PID-file) and -D (daemon mode) options to the utilities libraries.

Make varnishlog use these options.
Add signal handlers to utilities library for graceful shutdown
Rotate log on SIGHUP
Remove -D and -P "not yet implemented" messages from varnishlog.rst
Remove -u "not yet implemented" from varnishlog.rst
Implement -I and -X varnishlog options
Add vut_options to dist
Fix option RST generation dependant on rst2man to not make use of gnu
make order only prerequisites.