Make XENFIRMWAREDIR a subdir of libexecdir

Put the firmware files below libexecdir. This is essentially just a new
name for the existing path. It has the benefit that it can be configured
via --libexecdir= if required.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Move xenconsoled to libexec

xenconsoled is started by runlevel scripts, its not supposed to be
called by admin.  So move it out of the way into LIBEXEC_BIN.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Move xenstored to libexec

xenstored is started by runlevel scripts, its not supposed to be
called by admin.  So move it out of the way into LIBEXEC_BIN.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Move xenwatchdogd to libexec

xenwatchdogd is started by runlevel scripts, its not supposed to be
called by admin.  So move it out of the way into LIBEXEC_BIN.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
Remove unused exec_prefix from Paths.mk

Signed-off-by: Olaf Hering <olaf@aepfle.de>
rerun autogen.sh

Signed-off-by: Olaf Hering <olaf@aepfle.de>