rename service_resolve_svtree function to service_intree. Rename struct ss_resolve_graph_style to info_graph_style

allow to use a different version of configuration file than the frontend file if any of -c/m/C is providen. Version symlink point now to the directory instead of the file itself which allow to have extra configuration file

pass to new configuration location. Only read the configuration file of the service. Use the new ss_resolve_svtree()

deprecated -c option and use -z instead. This change is made to be consistent with option between tools

Prevent symbol lookup error in commands linked to lib66.so:

66-tree: symbol lookup error: /usr/x86_64-pc-linux-gnu/lib/lib66.so.0.2:
undefined symbol: MAXDEPTH

This reverts commit 4eb81994.

sys/unistd.h is not a standard header file, not found on musl system.
It is supposed to be unneeded.