Rewrite automake's data installation rules, because they suck.

Rewrite automake's data installation rules, because they suck.

Specifically, they didn't handle installing data from both srcdir and builddir.
We have the tutorial in the srcdir, and build the manual in the builddir.

Also, stop rebuilding the manual for each make target in the doc directory, and
every time any of those targets get called.  This change now makes the manual
never rebuild once built; we plan to fix that later, by rewriting the makefiles
to avoid recursive make, and then making the manual depend on the source files.

Commit by Jamey Sharp and Josh Triplett.