criu --help: fit to 80 columns

From where I stand, any help output that exceeds 80 columns is hardly
readable, so let's try to fit into that.

Apparently in many cases we can do that by removing some extra info
which, I guess, belongs to documentation or wiki but not to --help
output which should be just a short reference.

For this reason, this patch also removes information about environmental
variable set for external scripts -- such documentation does not belong
here.

Please review carefully to make sure I haven't thrown the baby out
with the bathwater.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

crtools.c

@@ -368,9 +368,9 @@ usage:
 "Dump/Restore options:\n"
 "\n"
 "* Generic:\n"
-"  -t|--tree PID         checkpoint/restore the whole process tree identified by PID\n"
+"  -t|--tree PID         checkpoint/restore a process tree identified by PID\n"
 "  -d|--restore-detached detach after restore\n"
-"  -s|--leave-stopped    leave tasks in stopped state after checkpoint instead of killing them\n"
+"  -s|--leave-stopped    leave tasks in stopped state after checkpoint\n"
 "  -R|--leave-running    leave tasks in running state after checkpoint\n"
 "  -D|--images-dir DIR   directory where to put images to\n"
 "     --pidfile FILE     write a pid of a root task to this file\n"
@@ -379,20 +379,17 @@ usage:
 "  -x|--" USK_EXT_PARAM "      allow external unix connections\n"
 "     --" SK_EST_PARAM "  checkpoint/restore established TCP connections\n"
 "  -r|--root PATH        change the root filesystem (when run in mount namespace)\n"
-"  --evasive-devices     use any path to a device file if the original one is inaccessible\n"
-"  --veth-pair IN=OUT    correspondence between outside and inside names of veth devices\n"
-"  --link-remap          allow to link unlinked files back when possible (modifies FS till restore)\n"
+"  --evasive-devices     use any path to a device file if the original one\n"
+"                        is inaccessible\n"
+"  --veth-pair IN=OUT    map inside veth device name to outside one\n"
+"  --link-remap          allow to link unlinked files back when possible\n"
 "  --action-script FILE  add an external action script\n"
-"                        The environment variable CRTOOLS_SCRIPT_ACTION contains one of the actions:\n"
-"                        * network-lock - lock network in a target network namespace\n"
-"                        * network-unlock - unlock network in a target network namespace\n"
 "  -j|--" OPT_SHELL_JOB "        allow to dump and restore shell jobs\n"
 "  -l|--" OPT_FILE_LOCKS "       handle file locks, for safety, only used for container\n"
 "\n"
 "* Logging:\n"
 "  -o|--log-file FILE    log file name (path is relative to --images-dir)\n"
-"     --log-pid          if the -o option is in effect, log of each restored process is\n"
-"                        written to a separate FILE.pid file\n"
+"     --log-pid          enable per-process logging to separate FILE.pid files\n"
 "  -v NUM                set logging level\n"
 "                          0 - messages regardless of log level\n"
 "                          1 - errors, when we are in trouble\n"