Re: pg_rewind in contrib

Here's an updated version of pg_rewind. The code itself is the same as
before, and corresponds to the sources in the current pg_rewind github
repository, as of commit a65e3754faf9ca9718e6b350abc736de586433b7. Based
mostly on Michael's comments, I have:

* replaced VMware copyright notices with PGDG ones.
* removed unnecessary cruft from .gitignore
* changed the --version line and "report bugs" notice in --help to match
other binaries in the PostgreSQL distribution
* moved documentation from README to the user manual.
* minor fixes to how the regression tests are launched so that they work
again

Some more work remains to be done on the regression tests. The way
they're launched now is quite weird. It was written that way to make it
work outside the PostgreSQL source tree, and also on Windows. Now that
it lives in contrib, it should be redesigned.

The documentation could also use some work; for now I just converted the
existing text from README to sgml format.

Anything else?

- Heikki