Reword the "linux" make target slightly

* Ensure that linux_v is always set, no matter what uname says.
* Use the $(shell) make function
* Remove quotes - they seem to not get interpolated for some reason.
* Use mkdir -p to make building work when the gem already has a "man"
  dir.

This fixes #406.
Merge pull request #405 from antifuchs/bump-fsevents-to-xcode5

Fix fsevents-wrapper settings so it builds on Xcode5
Fix "slave `boot` was killed", shorten backtraces

Extract command running from the `go` method. This ensures that the
process running the command never tries to re-register with the client
monitor on the Zeus side, which was what caused the "slave `boot` was
killed" messages mentioned in #410. This was originally broken by the
recursion elimination in #361 (turns out unrolling recursion is hard!).

As a pleasant side effect, this change also eliminates two more lines in
the `go` method from backtraces on commands.
Revert "We should really be using SOCK_STREAM, not SOCK_DGRAM."

This reverts commit 1ed167e80984a6dee4ca0e85be7b7ea55a70119c.
Resize SO_SNDBUF on unix sockets

This should ensure that no datagrams get truncated.
Record the zeus arguments on config.Args

This allows people to pass --log to zeus for running commands, and it
will output the trace log (and execute the right command), also.
Pass a pipe for args from zeus client to command

Instead of passing the command arguments from the zeus client to the
zeus master, and from there to the command process over their respective
sockets, create a streaming socket in the zeus client, pass that socket
over to the zeus master, have the zeus master pass it on to the command
process, and read the zero-separated arguments directly in the command.

This has a two advantages:

One, it supports unbounded numbers of arguments on Linux and OS
X (previous solutions only worked either on one or the other).

Two, it extracts all command argument handling from the zeus master -
all the master now does is pass a count and an FD from one pipe to
another.