Doc split to high-level-chain-mgr.tex finished

All of the major surgery required to move Chain Manager design & discussion
details out of the high-level-machi.tex document are complete.  I've done
only a very small amount of work on the original high-level-machi.tex to
fix document flow problems.

There's probably a good way to have LaTeX automatically manage the
mutual references between the now-split documents, but I didn't know about,
sorry.

doc/src.high-level/Makefile

@@ -1,6 +1,8 @@
 all:
 	latex high-level-machi.tex
 	dvipdfm high-level-machi.dvi
+	latex high-level-chain-mgr.tex
+	dvipdfm high-level-chain-mgr.dvi
 
 clean:
 	rm -f *.aux *.dvi *.log