* gdb.base/advance.c (marker1): New marker function.
* gdb.base/advance.exp: When the 'advance' command lands on the
return breakpoint, it can legitimately stop on either the
current line or the next line. Accommodate both outcomes.
* gdb.base/until.exp: Likewise.
* gdb.base/break.exp: Move the tests of until command from here...
* gdb.base/until.exp: ... to here. New file. Add other tests.
* gdb.base/advance.c: New file.
* gdb.base/advance.exp: New file.