lttng.ust: Retrieve the function name when calling addr2line

lttng.ust: Retrieve the function name when calling addr2line

Add the -f flag to also query function/symbol names. This will
allow us to populate the "function name" field of the generated
callsite objects, which in turn will populate the Callstack View
appropriately.

Also pass the -C flag, which demangles C++ function names, without
apparantly affecting native names.

Change-Id: Ife6e8581347ab2f94558e258dc350a4c1b04c3fa
Signed-off-by: Alexandre Montplaisir <alexmonthy@efficios.com>
Reviewed-on: https://git.eclipse.org/r/69971
Reviewed-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Tested-by: Matthew Khouzam <matthew.khouzam@ericsson.com>
Reviewed-by: Hudson CI