Closes #265.

For pselect() we want to mess with the signal mask, and this is closer to our
intent anyway.

Now that we have select.cc.

It's going to manipulate process-global signal state, so multiple
instances do not make sense.

Closes #235.

Fixes #264.

Fixes #271 github issue.

Saves battery power.  Closes #243.

Simplifies access to private data, including the next commit.

git renders this diff poorly.  It's a bit better with --patience.

So that UI timeouts can adjust accordingly.

This prevents the client from waking up every 200 ms while the network is down.
Addresses #243.

Fixes
  aclocal:configure.ac:22: warning: macro `AM_PROG_AR' not found in library
and
  ./configure: line 4024: AM_PROG_AR: command not found
with old automake.

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

Needed to build from our source tarball on some Gentoo systems.

Closes #239.
Closes #254.

Closes #253

Fixes vttest regression.

(closes #245)

This reverts commit f4c84176.

config.h was already included via base64.h, and problem is older autoconf.