Modified the compound event types getters to return existing fields

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Fix: Use the g_hash_table_lookup_extended to check for key existence

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Add the implementation of the CTF Writer Event API

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Change quark to index hash table name to make it more consistent with the ones used in the Event Types structures

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Remove the Event name accessor

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>