Introduce partial_symbol::address

Introduce partial_symbol::address

This introduces a partial_symbol::address method.  This method takes
an objfile argument.  This is necessary so that we can later relocate
a partial symbol at its point of use.  It also adds an accessor to
compute the unrelocated value; and a method to be used for setting the
field.

Note that the new method doesn't actually perform any relocation yet.
That will come in a subsequent patch.  However, the comments are
written to reflect the intended, rather than the temporary, semantics.

gdb/ChangeLog
2018-07-26  Tom Tromey  <tromey@redhat.com>

	* psympriv.h (struct partial_symbol) <unrelocated_address,
	address, set_address>: New methods.
	* psymtab.c (find_pc_sect_psymtab_closer, find_pc_sect_psymbol)
	(fixup_psymbol_section, relocate_psymtabs): Update.
	(print_partial_symbols): Add 'objfile' parameter.  Update.
	(dump_psymtab, add_psymbol_to_bcache, psym_fill_psymbol_map):
	Update.