Revision 418566

Import several patches recently merged upstream.

- Fix fork following to honor 'detach-on-fork'
- Fix vfork following to post a fake vfork_done event to fix breakpoints
  in vfork parents (a real vfork_done event is pending but requires kernel
  changes currently in review).
- Fix x86 debug registers to work with multiple threads (PR 157755)
- Add support for 'info auxv' on both live processes and cores.
- Add support for 'catch syscall'.  Note that catching system calls by
  names requires parsing an XML file mapping system call names to
  numbers.  The port now installs the XML syscall files to the data
  directory.  In addition, the EXPAT option is now enabled by default as
  expat is used to parse the XML files.
- Bump PORTREVISION.

PR:		157755, 210874
Approved by:	luca.pizzamiglio@gmail.com (maintainer), bdrewery