[PATCH] Outwit compiler dead code elimination in break.exp test

[Fred Fish]

> If you're there, rather than being the second person this month to
> update the line numbers, could you convert it to gdb_get_line_number?

OK, I'll take a look at that.

There may also be places where the line numbers are irrelevant for the
feature being tested ("maint info breakpoints" for example?) and could
just be replaced with patterns to check for any line number.

-Fred