As far as I know, for all implementations of libutempter, the
utempter_remove_added_record() function depends on the file descriptor
passed to utempter_add_record() to still be valid. The reason for this,
is that this file descriptor is propagated to the setuid utility that is
responsible for modifying utmpx.

Modify the code to remove the utmpx entry before closing the
pseudo-terminal master device. While there, simply use
utempter_remove_record(), which takes the file descriptor explicitly.
The advantage is that this prevents potential foot-shooting in the
future. Visual inspection of the source code will make it more obvious
that utempter depends on the file descriptor.

Closes #179.

[keithw -- applied style change from kmcallister]

Closes #181.

Closes #173.

Let users specify an ssh outside their PATH, or extra flags like -p or -i.

Modify the usage message to describe this feature and hint at the
semantic difference viz. --client=path\ to\ client vs --ssh="path\ to\
ssh".

Closes #53

[keithw@mit.edu -- applied fixes per Anders Kaseorg]

EL5 lacks htobe64 and friends.  Using its byteswap.h requires an endianness
check in our headers, which is fragile and compiler-dependent.  It's a fair
amount of code [1], and is only useful on EL5.

So instead, let's include a fallback implementation of these functions, and use
it whenever we can't find the (now-)standard Linux or OS X routines.  The
fallback is endianness-independent and should work on any platform.

[1] https://github.com/rurban/mosh/commit/da1a5abd1e09f0c1e9295357bb480a643d9dc8e3

Needed for EL5.

Based on:
https://github.com/rurban/mosh/commit/c70c3707e65b42ac9b9da937e9c255211330805e

It's reserved by POSIX.

(closes #158 pull request)

g++/libstdc++ 4.1.2 is unhappy with this use of bind2nd, possibly because the
argument is a reference.  This is a problem for EL5.

Fixes #74.

(should help #155 github issue)

May help some sufferers of #114 github issue.

Re: #137

Addresses #155 github issue.

Closes #170 github issue.

selfpipe already does a fine job of interfacing to signalfd.  But Debian and
Ubuntu want us to depend on the skalibs-dev package rather than build libstddjb
ourselves.  That would be fine except that skalibs-dev has static libraries
only, and they aren't built with -fPIC.  This interferes with building
mosh-{client,server} as position-independent executables, which is a desirable
security measure.

So we have our own wrapper, which invokes either signalfd or selfpipe.  And we
build it ourselves with our own flags, because it's part of the Mosh project
proper.

(closes #108)