core.c (core_close): Call CLEAR_SOLIB.
(core_open): Remove comment about "should deal with shared lib".
(core_xfer_memory): If we can't xfer the usual way, try the
shared libraries.
solib.c (so_list): New fields so_bfd and so_sections{,_end}.
(find_solib): Use solib_map_sections to get ld_text.
(solib_map_sections, solib_xfer_memory): New functions.
(clear_solib): Free so_sections and close so_bfd.
tm-sunos.h: Add solib_xfer_memory, solib_add.
target.c: Add target_preopen and target_command.
Remove target_info.
(add_target): Call add_cmd and mess with targetlist->doc.
core.c, exec.c, remote-eb.c, remote-nindy.c, remote-vx.c,
remote-vx.68.c, inftarg.c, remote.c: Add doc field to target struct.
Call target_preopen from open routine.
