* symfile.h (get_section_index): Define.

* symfile.h (get_section_index): Define.
* symfile.c (get_section_index): New function.
* mdebugread.c (SC_IS_SBSS): New macro.
(SC_IS_BSS): Return true for the scBss storage class only, as
the scSBss storage class refers to the .sbss section.
(parse_partial_symbols): Discard the symbols which associated
section does not exist.
Make sure to use the .sbss section index for symbols which
storage class is scBss, rather than using the .bss section index.