driver/ppm_events_public: change ppm_param_info.symbols in info.

Change ppm_name_value* symbols in void* info, so that we can store
extra informations for parameters which can have multiple
meanings/types depending on some other parameters.
driver: add PPME_SYSCALL_PTRACE_*
driver: handle request parameter of ptrace syscall
driver/ppm_fillers: add simple ptrace_x filler
start converting ptrace "addr" param to PT_DYN
driver: prepare fillers and val_to_ring to accept dyn_idx

TODO: implement PT_DYN type
implement PT_DYN in both driver and userspace
implement ptrace filler and parse some requests
driver/ppm_fillers: refactor ptrace_x filler
userspace/libsinsp/event: fix error when handling PT_DYN params
Merge branch 'master' into ptrace_filler2

Conflicts:
	userspace/libsinsp/event.cpp
Merge branch 'master' into ptrace_filler2

Conflicts:
	driver/event_table.c
	driver/flags_table.c
	driver/ppm_events.c
	driver/ppm_events_public.h
	driver/ppm_fillers.c
	userspace/libscap/CMakeLists.txt
	userspace/libscap/event_table.c
	userspace/libscap/flags_table.c
	userspace/libsinsp/event.cpp
Check if the dynamic index is in the valid range
Add a "verbose" module parameter that enables some extra logging (now disabled by default for Release builds)
typo
Remove obsolete --abstime option
a bunch more work on syslog
zlib was wrongly undefined
make sure sinsp_thread_manager::remove_thread doesn't bring the main thread reference counter below zero
bufix: extract the value before deciding to skip it in sinsp_evt_formatter::tostring