Allow build outside of read-only source tree.
Identify files that need to be included in the tarball. Also change some from Makefile.am entries to identify that are not in the tarball (since later generated during build). Includes needed for headers in src tree and in build tree (because some includes are generated). Also includes specifically for "dns" needed since headers in src tree don't see the ones in build tree and vice versa. Have the gen-rdatacode.py script read placeholder from src tree and save generated files into build tree. Okayed by Jinmei. Identify a few files that should be removed on a clean. git-svn-id: svn://bind10.isc.org/svn/bind10/trunk@1389 e5f2f494-b856-4b98-b285-d166d9295462