Properly handle 64-bit GOT relocations

This patch fixes 2 issues:

1. Since the GOT offset is always negative, we need to use signed int
to support 64-bit GOT relocations.
2. R_X86_64_PLTOFF64 uses the address of GLOBAL_OFFSET_TABLE, which is
the address of the .got.plt section, not the .got section.
Add new link-map-text hook and RX auto-vector support.

* bfd/elf32-rx.c (get_symbol_value_maybe): New.
(rx_elf_relocate_section): If we find a reloc against
$tableentry$default$<name>, redirect it to the appropriate
$tableentry$<n>$.
(RX_Table_Info): New.
(rx_table_find): New.  Check all tables and SEC_KEEP all sections
with table parts in them.
(rx_check_directives): New.
(rx_table_map_2): New.
(rx_table_map): New.
(rx_additional_link_map_text): New.  Called to dump tables to the
map file.
* bfd/elf32-rx.h: New.

* ld/ldemul.h (extra_map_file_text): New field.
(ldemul_extra_map_file_text): Declare.
* ld/ldemul.c (ldemul_extra_map_file_text): Define.
* ld/ldlang.c (lang_map): Call it.

* ld/emultempl/rxelf.em: Add extra_map_file_text hook.
* ld/emultempl/aix.em: Add NULL extra_map_file_text hook.
* ld/emultempl/armcoff.em: Likewise.
* ld/emultempl/beos.em: Likewise.
* ld/emultempl/elf32.em: Likewise.
* ld/emultempl/generic.em: Likewise.
* ld/emultempl/gld960.em: Likewise.
* ld/emultempl/gld960c.em: Likewise.
* ld/emultempl/linux.em: Likewise.
* ld/emultempl/lnk960.em: Likewise.
* ld/emultempl/m68kcoff.em: Likewise.
* ld/emultempl/pe.em: Likewise.
* ld/emultempl/pep.em: Likewise.
* ld/emultempl/sunos.em: Likewise.
* ld/emultempl/ticoff.em: Likewise.
* ld/emultempl/vanilla.em: Likewise.