MFC r258873: Workaround lldb issue with main module base address

MFC r258873: Workaround lldb issue with main module base address

  On FreeBSD lldb sometimes reloads the the main module's (executable's)
  symbols at the wrong address.  Work around this for now by explicitly
  reloading at base_address=0 when it happens.

  A proper fix is needed but early testers have reported this issue so
  this workaround should allow them to make further progress.

  http://llvm.org/bugs/show_bug.cgi?id=17880

Sponsored by:	DARPA, AFRL

git-svn-id: svn://svn.freebsd.org/base/stable/10@263366 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f