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>

llvm-svn: 223565