Push directives over literal chunks when attempting to move them to
the following chunk on x86.  Occasionally gcc generates a .glob
directive some distance before the symbol it refers to, and we were
ending up with a whole load of .glob directives attached to strings,
and duplicated in each .o file when splitting.

This change reduces the size of my libHSstd_p.a from 43M (!!!) to 9M.
I think this problem must have appeared with gcc 2.95.2, but it's a
little strange that I didn't notice it until now.