* module/language/tree-il.scm (<tree-il>): Add `pre' and `post' fields
to <dynwind>, so that we can inline the guard bodies in the normal
control-flow case. It also avoids duplicating code in compile-glil,
which probably hides more bugs in 2.0.
(parse-tree-il, unparse-tree-il, tree-il->scheme, tree-il-fold)
(make-tree-il-folder, post-order!, pre-order!): Update.
* module/language/tree-il/analyze.scm (analyze-lexicals): Update.
* module/language/tree-il/compile-glil.scm (flatten-lambda-case): Update
to use `pre' and `post' instead of compiling code twice.
* module/language/tree-il/debug.scm (verify-tree-il): Update.
* module/language/tree-il/peval.scm (peval): Update. Instead of doing
complicated things in <dynwind>, handle 'dynamic-wind primcalls.
* module/language/tree-il/primitives.scm (*primitive-expand-table*):
Remove 'dynamic-wind mess. Adapt '@dynamic-wind.
* test-suite/tests/tree-il.test ("partial evaluation"): Update tests.
