restore_term_settings: add warning message about SIGWINCH and Apache

This patch adds a warning in restore_term_settings() for
users testing DMTCP with Apache. Users should disable
the SIGWINCH that DMTCP sends on restart because Apache
uses that as a signal for terminating gracefully.

Future patches can include a method to do this automatically
by wrapping the call to send SIGWINCH in an ifdef that gets
disabled with a configure option.
restore_term_settings: add warning message about SIGWINCH and Apache

This patch adds a warning in restore_term_settings() for
users testing DMTCP with Apache. Users should disable
the SIGWINCH that DMTCP sends on restart because Apache
uses that as a signal for terminating gracefully.

Future patches can include a method to do this automatically
by wrapping the call to send SIGWINCH in an ifdef that gets
disabled with a configure option.
exit wrapper: add comment about tgkill(SIGUSR2)

This patch adds a comment in the DMTCP exit wrapper in
miscwrappers.cpp about the tgkill(SIGUSR2) that is sent to
the ckpt thread when a user application thread under DMTCP
calls exit().
Merge branch 'apache-bbn' of https://github.com/dmtcp/dmtcp into apache-bbn

Conflicts:
	src/terminal.cpp
restore_term_settings: change warning for SIGWINCH to comment

Based on Kapil's comments (https://github.com/dmtcp/dmtcp/pull/7/)
Merge pull request #7 from dmtcp/apache-bbn

Lessons from trying to checkpoint Apache
Detect that we explicitly call "srun". If PMI is used in this case - we deal with internal PMI and there is no need to shut it down.
We need to shutdown only for SLURM PMI where we can't control all processes (srun for example), int this case we call program like this:
$ srun dmtcp_launch --rm <other-dmtcp-opts> ./mpi-application
So we call srun implicitly and the flag won't be up.
[RM plugin] add --explicit-srun flag to "srun dmtcp_launch ..." command.
Merge pull request #8 from artpol84/master

Fix PMI shutdown problem with Hydra PMI
Buf fix: dmtcp_launch.cpp: fails when number of parameters exceeds 128
Fix --join for dmtcp_launch and dmtcp_restart.
HYDRA PMI: Fix logical expression that determines whether we want PMI shutdown or not.
Merge pull request #10 from artpol84/hydra_pmi

HYDRA PMI: Fix logical expression that determines whether we want PMI sh...
[RM plugin] cleanup slurm component: close fd after env restore.
Merge pull request #11 from artpol84/fix_slurm

[RM plugin] cleanup slurm component: close fd after env restore.
Allow MTCP_RESTART_PAUSE again (as in DMTCP-2.1)
Fix MTCP_RESTART_PAUSE; add MTCP_RESTART_PAUSE2
Advanced SLURM srun handling. Differentiate between Open MPI's ORTE and MPICH's hydra.
Fix for srun support commit.
1. Change some asserts to JASSERS
2. Fix abstract unix sockets.
MTCP: Minor fix to print errno on error.