env, stack, and operand_stack are linked lists
add W_EvalCall, because both operate and eval have to be flattened into the loop
tests
strings (for debugging)
change
properly stack environments
ignore wrap for now
Revert "towards eliminating m_evals"

This reverts commit 233eecccbdd8398c5b20166db991dddd40357a70.
Merge branch 'master' of git://github.com/timfel/qoppy

* 'master' of git://github.com/timfel/qoppy:
  ignore wrap for now
  properly stack environments
  change
  strings (for debugging)
  tests
  add W_EvalCall, because both operate and eval have to be flattened into the loop
  env, stack, and operand_stack are linked lists