* solib.c (master_so_list): Likewise.
* solib-svr4.c (enable_break): Iterate over so_list entries
obtained from master list instead of entries obtained directly
via svr4_current_sos().
* solist.h: Declare new function solib_open.
* solib.c (solib_open): New function. Abstracts some of the
code from solib_map_sections, for finding the binary solib file.
(solib_map_sections): Call solib_open.
* solib-svr4.c (enable_break): Call solib_open.