tmf: Handle spaces in function names in the Callstack View

tmf: Handle spaces in function names in the Callstack View

De-mangled C++ symbol names may contain spaces, so the function
name reader must not split around these spaces.

Also mention in the documentation that 'nm --demangle' can be used
to get readable C++ function names.

Refs bug #459534.

Change-Id: Ib046a15ada590b389bb8d1af2983e00629d17a35
Signed-off-by: Alexandre Montplaisir <alexmonthy@voxpopuli.im>
Reviewed-on: https://git.eclipse.org/r/41561
Reviewed-by: Hudson CI
Reviewed-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>
Tested-by: Marc-Andre Laperle <marc-andre.laperle@ericsson.com>