1.  Fix a defect in `>%class%` handling;  I was assuming that `szmarkerclass()
    would always return 3 (id:) or 6 (class:), when it actually returns
    0 (implied class:), 3 (id:), or 6 (class:) -- this assumption meant that
    the construct `>%class%` wouldn't generate enough room for the class="class"
    style fragment, which meant that properly paranoid malloc()s [like the one
    used by visual c++ 6] would puke and die on it.

2.  Add `$(DESTDIR)` to all of the make install stanzas, so it's easier for
    a packaging tool to build up the code, install it into a sandbox, then
    tar up the sandbox ready for installing.