Import pgindent.

Import pgindent.

Import PostgreSQL's pgindent.

This commit not only imports PostgreSQL's pgindent, but generates the
important file: typedefs.list. For this purpose followings are added:

- README.pgpool: How to generate typedefs.list.

- doxygen.list: Pgpool-II's typedefs extracted by doxygen. Plus
  manually added typedefs that were not detected by doxygen.

- enums.list: Pgpool-II's enums manually extracted from source code.

- exclude_files: files that should not be touched pgindent.

- run_pgindent: handy script to run pgindent. Should be run at src
  directory.

- typedefs.list.PostgreSQL: PostgreSQL's typedefs. To prepare for that
   doxygen misses some typedefs.

- make_typedefs.list: handy script to generate typedefs.list.