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
Handle enable_event command with instrument target

Define a structure holds the event instrument target data. The last
data item is a flexible array that contains a variable number
of target path.

Add instrument target data to the prototype of cmd_enable_event(),
and process the instrument target data form clients in the function.

Add error codes of processing instrument traget data.

Conflicts:
	include/lttng/lttng-error.h
	src/bin/lttng-sessiond/main.c
Handle instrument target in cmd_enable_event()

Add instrument target data to the prototype of event_ust_enable_tracepoint().
Handle instrument target in event_ust_enable_tracepoint()

Add instrument target data to the prototype of trace_ust_create_event()
and trace_ust_find_event().

Update the test_ust_data unit test with the new prototype.
Handle instrument target in trace_ust_create_event()

Copy instrument target and probe information from client.

Free allocated instrument target data when destroying events.

Also remove unused LTTNG_EVENT_FUNCTION_ENTRY event type.

Conflicts:
	src/bin/lttng-sessiond/trace-ust.c
Handle instrument target in trace_ust_find_event()

Add instrument target as a ltt_ust_ht_key and handle it in function
trace_ust_ht_match_event() and add_unique_ust_event().
Add 'dynamic-inst-release' to travis-ci
Add unit test for enabling events with instrument target