Add live trace reading support to lttvtraceread lib

Add support to read trace that were not previously closed. Useful to
read live trace or incorrectly closed trace.  Support the opening of
incomplete tracefile and its delayed initialisation Rework the block
index management Add a ltt_tracefile_update, ltt_trace_update and
ltt_trace_open_live interface JNI interface for ltt_openTraceLive and
ltt_updateTrace

Update: Remove dead code and fix const correctness

Signed-off-by: Yannick Brosseau <yannick.brosseau@gmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>