[katcp] Add --always to git describe command

If the repo has no tags, then git describe will fail unless --always is
given.
[katcp] Add a "show" target to katcp/Makefile

Running "make show" in the katcp subdirectory will print out the values
that will be used for VERSION and BUILD.
[katcp] Force katcp's BUILD timestamp to be UTC

Also include "UTC" timezone designator at the end of the string.  This
adds whitespace in the BUILD string (e.g. "2013-04-03T05:34:59 UTC")
which complicates the passing of the BUILD string since it was wrapped
in double quotes that were escaped from the shell and passed through to
the compiler (to make the macro expand to a double quated string).  This
is addressed by NOT escaping the quotes from the shell and then
stringifying the macro text using a new preprocessor macro named
STRINGIFY (defined in katcp/katcp.h, see comments there for more info).
Add .gitignore

Keeps "git status" a little quieter.
[tcpbs3] Append -$(GITVER) to tcpborphserver3 name

When building the "all" (i.e. default) target in the tcpborphserver3
subdirectory, the tcpborphserver3 executable file's name has a
"-$(GITVER" suffix.  The Makefile now includes an explicit
"tcpborphserver3" target which simply copies the suffixed file to
an un-suffixed "tcpborphserver3" file.  People wishing to create
un-suffixed executables should use "make tcpborphserver3".