virsh: Split cmds of storage volume group from virsh.c

This splits commands of storage volume group into virsh-volume.c,
The helpers not for common use are moved too. Standard copyright
is added for the new file.

* tools/virsh.c:
  Remove commands for storage storage volume and a few helpers.
  (vshCommandOptVol, vshCommandOptVolBy).

* tools/virsh-volume.c:
  New file, filled with commands of storage volume group and its
  helpers.

* po/POTFILES.in:
  Add virsh-volume.c

* cfg.mk:
  Skip to check config.h including for virsh-volume.c

cfg.mk

@@ -773,7 +773,7 @@ exclude_file_name_regexp--sc_prohibit_xmlURI = ^src/util/viruri\.c$$
 
 exclude_file_name_regexp--sc_prohibit_return_as_function = \.py$$
 
-_virsh_includes=(edit|domain-monitor|domain)
+_virsh_includes=(edit|domain-monitor|domain|volume)
 exclude_file_name_regexp--sc_require_config_h = ^(examples/|tools/virsh-$(_virsh_includes)\.c$$)
 
 exclude_file_name_regexp--sc_require_config_h_first = ^(examples/|tools/virsh-$(_virsh_includes)\.c$$)

po/POTFILES.in

@@ -180,6 +180,7 @@ tools/virsh.c
 tools/virsh-domain-monitor.c
 tools/virsh-domain.c
 tools/virsh-edit.c
+tools/virsh-volume.c
 tools/virt-host-validate-common.c
 tools/virt-host-validate-lxc.c
 tools/virt-host-validate-qemu.c