merge ProofTreeBranch into main trunk:

- add support for proof-tree displays (currently Coq only)
- new file generic/proof-tree.el contains generic code
- Coq specific code has been added to coq/coq.el

Changes to existing Proof General functions:
- proof-shell-exec-loop and proof-shell-filter-manage-output call
  proof-tree display functions, when the proof-tree display is on
- proof-shell-exec-loop returns t if proof-action-list is empty
  _or_ contains only items for updating the proof-tree
- proof-shell-should-be-silent returns nil when the proof-tree
  display is on
- coq-last-prompt-info, coq-last-prompt-info-safe return as
  additional 4th element the name of the current proof

1 files changed, 0 insertions, 0 deletions

diff --git a/images/epg-prooftree.png b/images/epg-prooftree.png
new file mode 100644
index 00000000..0de55213
--- /dev/null
+++ b/images/epg-prooftree.png