Check magic cookies between remote endpoints (#22)

The idea here is to ensure endpoints are properly paired by exchanging
a "cookie." If the source side cookie and destination side cookie
don't match then the transfer will fail immediately. Our inspiration
is XWindows and MIT-MAGIC-COOKIE-1.

This feature won't be useful until the cookie can be set by a command
line option.
Add a '-cookie' CLO to set the magic cookie (#22)

This commit fixes #22.
Merge pull request #40 from ORNL/fix-22

Fix #22
Clean up XNI memory registration functions

Removes an extraneous parameter to xni_register_buffer(). Removes
xni_unregister_buffer() because it was unused and unimplemented.
Add helper function to test for end-to-end
Allocate I/O buffers in the target thread

Previously the I/O buffers were allocated in the worker threads. This
commit is a necessary first step for fixing end-to-end connections
with XNI.

Except that this commit breaks end-to-end transfers.
Remove unnecessary e2e header fields

The whole e2e header will be moving to XNI soon. But before then I
want to make the header as small as possible.
Make XNI use network byte order for all messages
Use the correct byte conversion function

The wire protocol won't change (htonll(x) == ntohll(x)), but of course
it's always better to use the correct function for documentation
purposes.
Send the operation sequence number with XNI

The goal is to remove the xdd_e2e_header by sending the important
information in the XNI message header.
Fix infinite recursion bug
XNI: store target buffers in the connection

Target buffers are now allocated by the client but registered by
xni_accept_connection() or xni_connect().

Now that target buffers have moved from the xni_context to the
xni_connection we should be able to easily open multiple
connections. With multiple connections we should be able to support
multiple NICs.
Heartbeat fixed on destination side.
Fix -datapattern random regression

All of the datapatterns were broken and this commit fixes them.
Fixes #43.
Fix minor autoconf thing

The checks for patch and tar didn't really fail the configure, now
they do.
Fix #41 gitignore issue

Clean up paths, and extraneous ignore file.
Fix #33 make check fails sometimes

Make check now has dependencies that are a little better seperated,
and

make clean
make check

succeeds.
Fix #36 Verify doesn't work

Verify has never worked.  So fo rnow, make that option invisible.
There is no plan to re-enable it.
Modified the flow to put heartbeat options on the sink. And, password prompt uses the machine name given by the user.
Updated unit tests to accommadte the changes to xddmcp.