buildtools: detect discrepancies for experimental symbols

buildtools: detect discrepancies for experimental symbols

When promoting those symbols as stable, there is no check to ensure that
the final result is consistent.

Add a little script to get the symbols per section from the library map
files.
Validate that all experimental symbols in object files are referenced by
library map files.

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>