Pmake tutorial in SGML

[Giorgos Keramidas]

Hi all,

Some time ago, Oliver Fischer did a conversion of the Pmake tutorial to
SGML and submitted it as PR docs/62116.  I have made a few changes to
the original submission of Oliver (like adding a few SGML tags here and
there, etc) and tested the build of the book.  The diff from today's
doc/ tree is at:

http://people.freebsd.org/~keramida/diff/pmake.diff.bz2

Does this look like a valuable addition to our books?

- Giorgos