fix else in cond, letrec env corruption, syntax.scm compile, define-module side effects

* module/language/scheme/translate.scm (primitive-syntax-table):
  Translate the `else' clause of a cond as (begin ...). We used to use
  trans-body, which processes internal defines, which are not legal
  syntax here.

* module/system/base/syntax.scm (define-record): Unfortunately, we can't
  unquote in the actual procedure for `%compute-initargs', because that
  doesn't work with compilation. So reference %compute-initargs by name,
  and export it.

* module/system/il/ghil.scm (apopq!): Gaaaaar. The order of the arguments
  to assq-remove! was reversed, which was the badness, causing corruption
  to the env after calling call-with-ghil-bindings. Grrrrrr.

  (fix-ghil-mod!, ghil-lookup, ghil-define): As amply commented in the
  code, deal with compile-time side effects to the current module by
  lazily noticing and patching up the compile-time environment. A hacky
  solution until such a time as we special-case something for
  `define-module'.

module/language/scheme/translate.scm

@@ -203,7 +203,7 @@
    (cond
     ;; (cond (CLAUSE BODY...) ...)
     (() (retrans '(begin)))
-    (((else . ,body)) (trans-body e l body))
+    (((else . ,body)) (retrans `(begin ,@body)))
     (((,test) . ,rest) (retrans `(or ,test (cond ,@rest))))
     (((,test => ,proc) . ,rest)
      ;; FIXME hygiene!