Add the ability to set breakpoints with conditions, commands, etc,
in the "dummy-target".  The dummy target breakpoints prime all future
targets.  Breakpoints set before any target is created (e.g. breakpoints
in ~/.lldbinit) automatically get set in the dummy target.  You can also
list, add & delete breakpoints from the dummy target using the "-D" flag,
which is supported by most of the breakpoint commands.

This removes a long-standing wart in lldb...

<rdar://problem/10881487>


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@223565 91177308-0d34-0410-b5e6-96231b3b80d8