write.c: Complain about .space or .org moving backwards.

write.c: Complain about .space or .org moving backwards.

Do generic rs_machine_dependent relaxation only if TC_GENERIC_RELAX_TABLE is
defined.  Use its value as the base of the table, so the actual declaration
can be cpu-specific (and const or not as appropriate).  For other cpus where
this isn't done (the majority), delete md_relax_table altogether.

For machines with WORKING_DOT_WORD, delete md_{short,long}_jump_size.