libxl: use vchan for QMP access with Linux stubdomain

Access to QMP of QEMU in Linux stubdomain is possible over vchan
connection. Handle the actual vchan connection in a separate process
(vchan-socket-proxy). This simplified integration with QMP (already
quite complex), but also allows preliminary filtering of (potentially
malicious) QMP input.
Since only one client can be connected to vchan server at the same time
and it is not enforced by the libxenvchan itself, additional client-side
locking is needed. It is implicitly implemented by vchan-socket-proxy,
as it handle only one connection at a time. Note that qemu supports only
one simultaneous client on a control socket anyway (but in UNIX socket
case, it enforce it server-side), so it doesn't add any extra
limitation.

libxl qmp client code already has locking to handle concurrent access
attempts to the same qemu qmp interface.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>

Squash in changes of regenerated autotools files.

Kill the vchan-socket-proxy so we don't leak the daemonized processes.
libxl__stubdomain_is_linux_running() works against the guest_domid, but
the xenstore path is beneath the stubdomain.  This leads to the use of
libxl_is_stubdom in addition to libxl__stubdomain_is_linux_running() so
that the stubdomain calls kill for the qmp-proxy.

Also call libxl__qmp_cleanup() to remove the unix sockets used by
vchan-socket-proxy.  vchan-socket-proxy only creates qmp-libxl-$domid,
and libxl__qmp_cleanup removes that as well as qmp-libxenstat-$domid.
However, it tolerates ENOENT, and a stray qmp-libxenstat-$domid should
not exist.

Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

docs/configure

@@ -634,7 +634,6 @@ infodir
 docdir
 oldincludedir
 includedir
-runstatedir
 localstatedir
 sharedstatedir
 sysconfdir
@@ -711,7 +710,6 @@ datadir='${datarootdir}'
 sysconfdir='${prefix}/etc'
 sharedstatedir='${prefix}/com'
 localstatedir='${prefix}/var'
-runstatedir='${localstatedir}/run'
 includedir='${prefix}/include'
 oldincludedir='/usr/include'
 docdir='${datarootdir}/doc/${PACKAGE_TARNAME}'
@@ -964,15 +962,6 @@ do
   | -silent | --silent | --silen | --sile | --sil)
     silent=yes ;;
 
-  -runstatedir | --runstatedir | --runstatedi | --runstated \
-  | --runstate | --runstat | --runsta | --runst | --runs \
-  | --run | --ru | --r)
-    ac_prev=runstatedir ;;
-  -runstatedir=* | --runstatedir=* | --runstatedi=* | --runstated=* \
-  | --runstate=* | --runstat=* | --runsta=* | --runst=* | --runs=* \
-  | --run=* | --ru=* | --r=*)
-    runstatedir=$ac_optarg ;;
-
   -sbindir | --sbindir | --sbindi | --sbind | --sbin | --sbi | --sb)
     ac_prev=sbindir ;;
   -sbindir=* | --sbindir=* | --sbindi=* | --sbind=* | --sbin=* \
@@ -1110,7 +1099,7 @@ fi
 for ac_var in	exec_prefix prefix bindir sbindir libexecdir datarootdir \
 		datadir sysconfdir sharedstatedir localstatedir includedir \
 		oldincludedir docdir infodir htmldir dvidir pdfdir psdir \
-		libdir localedir mandir runstatedir
+		libdir localedir mandir
 do
   eval ac_val=\$$ac_var
   # Remove trailing slashes.
@@ -1263,7 +1252,6 @@ Fine tuning of the installation directories:
   --sysconfdir=DIR        read-only single-machine data [PREFIX/etc]
   --sharedstatedir=DIR    modifiable architecture-independent data [PREFIX/com]
   --localstatedir=DIR     modifiable single-machine data [PREFIX/var]
-  --runstatedir=DIR       modifiable per-process data [LOCALSTATEDIR/run]
   --libdir=DIR            object code libraries [EPREFIX/lib]
   --includedir=DIR        C header files [PREFIX/include]
   --oldincludedir=DIR     C header files for non-gcc [/usr/include]