Be less strict about named and unnamed arguments.

Recent GDB versions can report multiple breakpoints
but do so using an invalid MI format, see e.g. the
upstream bug report:
http://sourceware.org/bugzilla/show_bug.cgi?id=9659

Since we cannot expect GDB to be fixed anytime soon,
just make our parser less strict. This was actually
the recommendation in #gdb on freenode IRC as well...

BUG: 304730