* gdb.base/sepdebug.exp: Bail out of the test if we don't know
what debug info we have. Print a better message if something goes
wrong while producing the separate debug info file.
* gdb.base/sepdebug.exp: New file.
* gdb.base/sepdebug.c: New file.
* lib/gdb.exp (separate_debug_filename): New procedure.
(gdb_gnu_strip_debug): New procedure.