[gdb] Handle .TOC. sections during gdb-compile for rs6000 target.

[gdb] Handle .TOC. sections during gdb-compile for rs6000 target.

[gdb] Handle .TOC. sections during gdb-compile for rs6000 target.

  When we encounter a .TOC. symbol in the object we are loading,
we need to associate this with the .toc section in order to
properly resolve other symbols in the object.  IF a .toc section
is not found, iterate the sections until we find one with the
SEC_ALLOC flag.  If that also fails, fall back to using
the *ABS* section, pointed to by bfd_abs_section_ptr.