The minimal XML returned from ncf_if_xml_state() doesn't contain this
attribute (which makes no sense in the case of reporting current
status of the interface), and it was preventing it from passing
through the parse/format step.

* src/conf/interface_conf.[ch]: add a new virInterfaceStartMode value
  and modify loading/saving accordingly

* src/conf/interface_conf.c: This was causing subsequent calls to
  virXPathxxx() to fail, since ctxt->node was left pointing at the
  dhcp node, rather than the protocol node.

* src/capabilities.c, src/capabilities.h, src/domain_conf.c,
  src/domain_conf.h, src/domain_event.c, src/domain_event.h,
  src/interface_conf.c, src/interface_conf.h,
  src/network_conf.c, src/network_conf.h, src/node_device_conf.c,
  src/node_device_conf.h, src/secret_conf.c, src/secret_conf.h,
  src/storage_conf.c, src/storage_conf.h, src/storage_encryption_conf.c,
  src/storage_encryption_conf.h: Move to src/conf/
* src/Makefile.am: Add -Isrc/conf to the individual build targets
  which need to use XML config APIs. Remove LIBXML_CFLAGS, LIBSSH2_CFLAGS
  and SELINUX_CFLAGS from global INCLUDES and only have them in build
  targets which actually need them.  Create a libvirt_conf.la
  convenience library for all config parsers
* src/hostusb.h: Remove bogus include of domain_conf.h
* tests/Makefile.am: Add -Isrc/conf. Remove bogus -I$builddir/src
  since it never has any generated header files
* daemon/Makefile.am: Add -Isrc/conf
* proxy/Makefile.am: Add -Isrc/conf and cope with renamed files
* src/hash.c: Remove bogus include of libxml/threads.h

* src/interface_conf.c (virInterfaceDefParseDhcp): Remove unused "old".

* src/datatypes.c src/domain_conf.c src/interface_conf.c
  src/lxc_driver.c src/qemu_driver.c src/storage_backend.c src/virsh.c:
  add bare %s format string to printf-derivatives called with no format
  string

* qemud/remote.c src/interface_conf.[ch] src/veth.[ch]: more renaming
  from interface to iface

* interface_conf.c interface_conf.h: utilities function usful for
  interface driver like the test interface driver

* src/interface_conf.c src/interface_conf.h: the import and export
  routines and the internal APIs
* src/Makefile.am: hook the new file in the makefiles
* src/libvirt_private.syms: export a few private symbols internally
* po/POTFILES.in: the new file contains translatable strings