Added patch for Postgres 9.3 beta 2

This patch forces Postgres to pause after applying each WAL segment.
That enables Marty to inspect the newly applied content from the WAL
without the WAL replay process being able to overwrite the content with
new data from the WAL.

Copy to root of Postgres source directory and apply with
$ patch -p1 < marty.patch
Then compile with WAL debugging enabled.