* symfile.c (symbol_file_add_with_addrs_or_offsets): New function,

like the old symbol_file_add, but taking new arguments: you can
now pass in either a `struct section_addr_info' list to say where
each section is loaded, or a `struct section_offsets' table.  Pass
these new arguments through to syms_from_objfile as appropriate.
(symbol_file_add): Just call symbol_file_add_with_addrs_or_offsets,
with the appropriate quiescent values for the new arguments.

* symfile.c: #include "gdb_assert.h".
(syms_from_objfile): Add the ability to pass in a section offset
table directly, as an alternative to the section_addr_info table.
Document arguments better.
(symbol_file_add): Pass extra arguments to syms_from_objfile.
* symfile.h (syms_from_objfile): Update declaration.
* rs6000-nat.c (objfile_symbol_add): Pass new arguments to
syms_from_objfile.
* Makefile.in (symfile.o): List dependency on $(gdb_assert_h).