Memory abuse fix: StackFrame's ->frame may be unset.

Need to initialize it (and assert we're not stomping an old value in
the one place that does set it), as well as free()ing it later.
Leak-fix: free( ->comment) before over-writing it.

It's been set earlier to an xstrdup(), so simply assigning another to
it is negligent.
Fix bogus "return" in void Prefix##SetClear().

The type-specific variant of SetClear was returning SetClear, except
that they're both void.  Many compilers cope with that, but apparently
a user had problems building on Solaris because of it.
Leak-fix: DeletePackageManagers() missed two members.

Need to also delete the patch_list and patch_avail, as well as the
pack_list.
Merge pull request #1454 from ediosyncratic/leak-fixes

Leak fixes