PSpec S becomes s.

mfj= now works

Repaired bug introduced on 26oct: by default, zentries are unprotected

  while rewriting file selection in pimpl style

Refactored; basics moved to libtrivia

  exe/ls-includes.rb

- throw error on "cv -1", and more generally when tree_uival gets negative index
- infer k for c[]

  below the plot (in the PS output)