This is more stylistic than substantial, but it's bad enough
style to be worth fixing.

We were potentially passing (char *)NULL to string constructors.

I think this one was actually impossible to trigger.

Should resolve https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=811579

Resolves #719.

For example, do not interpret regex metacharacters within the
hostname, and avoid accidentally matching the username part of
username@hostname when they happen to match.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

Improves 679b8192 to make it simpler to
ignore mosh-client from OS X Terminal.app's "Ask before closing" process
list. (See: http://superuser.com/a/254647)

Moreover, the command displayed from ps is a completely functional one,
which was not the case in the previous approach, that mangles `argv[0]`.

Fixes #742.

Motivated by Cygwin.

Fixes #745.

There are (broken) compilers out there that accept -fstack-protector-*
parameters, but do not provide the needed ssp library. As a result,
build does not fail, but link does. Use the local check_link_flag
autoconf function to correctly test for SSP availability.

Required for the Imagination Technologies Codescape IMG MIPS
toolchain, version 2015.10 (and who knows what else).

Fixes #744.

This should resolve mobile-shell/mosh#675

Found by OpenBSD build.

* A resize action could be applied to the framebuffer but discarded
  before being applied to termios, causing them to be out of sync.

* Only every second action was skipped, instead of skipping
  consecutive resize actions, as intended.

Found by inspection, not seen in actual usage or by the window-resize
test.

This is an alternate way to resolve #417 without affecting
backward compatibility.

Add --family=auto/all.
Attempt connects to all available addresses.
Working error handling.

Fixes #629.

protobuf uses an obsolete automake pthreads detection macro,
which results in "pkgconfig --libs protobuf" returning
"-lprotobuf -pthread -lpthread" on Linux.  Remove
the unnecessary and dangerous -lpthread in that case.

Fixes #727, mosh-server crash in libutempter on Debian Sid.