x86, relocs: When printing an error, say relative or absolute

commit 24ab82bd9bf18f3efc69a131d73577940941e1b7 upstream.

When the relocs tool throws an error, let the error message say if it
is an absolute or relative symbol.  This should make it a lot more
clear what action the programmer needs to take and should help us find
the reason if additional symbol bugs show up.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>