ctags: include symbols with locking annotations.

ctags: include symbols with locking annotations.

OVS uses extensively clang annotations for thread safety
checks. The ctags tool can't parse them, so they are not
included in the tag file.

This patch improves the configure script to generate a list
of identifiers from the header compiler.h to be ignored by
ctags.

Signed-off-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: Ben Pfaff <blp@ovn.org>
Reviewed-by: Aaron Conole <aconole@redhat.com>