Removing the 'doc' dir, we have better docs in the wiki

Author: drotiro

README.md

@@ -33,7 +33,6 @@ This package contains the following:
  * __server__: sources for the server extension
  * __utils__: utilities for client-side loading of images, etc.
  * __jdbc__: mapping for the new type, enhances the postgresql jdbc driver
- * __doc__: instruction for building the sources
  * __examples__: example programs and sql scripts