Send enable-event commands with instrument target

Create a static function enable_event() to deal with all possible
permutations of data that accompany with the enable-event command:
- all events / some events
- no filter / a filter
- no exclusions / some exclusions
- no instrument target / a instrument target

Wrap existing functions lttng_enable_event(),
lttng_enable_event_with_filter() and lttng_enable_event_with_exclusions()
with the new static enable_event() functions without breaking API.

Create a new lttng_enable_event_with_target() function to handle the
instrument target data. Note that it is not possible to enable events
with excusions together with instrument target, since exclusions only
work with wildcard events.

Conflicts:
	src/lib/lttng-ctl/lttng-ctl.c
Parse and forward instument probes

Report error if userspace probes created with wildcard events.

Conflicts:
	src/bin/lttng/commands/enable_events.c
Add usage for userspace instrumented probes

Conflicts:
	src/bin/lttng/commands/enable_events.c