Set up the game to distribute PDF and HTML helpfiles where possible.

Set up the game to distribute PDF and HTML helpfiles where possible.  Closes #12.

* Adjust the buildsystem to build and install the docs.
* The OS X dist target and scripts/pkg_win include doc/manual.(pdf|html) when they exist.
* Make dist has been added to the root makefile, which tries to make the manual before packaging up the game with the manuals so generated (this should now replace scripts/pkg_src).