add separate expansion phase, to detwingle things a bit

* module/language/scheme/expand.scm: New module, implements a separate
  expansion phase, not interleaved with compilation.

* module/language/scheme/amatch.scm: Helper for expand.scm, it's pmatch
  with support for annotated source.

* module/ice-9/Makefile.am (SOURCES): Add annotate.scm to build list --
  early on because it will be used in the compiler.

* module/ice-9/annotate.scm: Fix the printer, default to unstripped
  (whatever that is), and add a deannotator.

* module/system/base/compile.scm (call-with-compile-error-catch): Fix for
  new representation of source locations.

* module/Makefile.am (SCHEME_LANG_SOURCES): Add amatch and expand.

module/language/scheme/amatch.scm

@@ -0,0 +1,37 @@
+(define-module (language scheme amatch)
+  #:use-module (ice-9 syncase)
+  #:export (amatch apat))
+;; FIXME: shouldn't have to export apat...
+
+;; This is exactly the same as pmatch except that it unpacks annotations
+;; as needed.
+
+(define-syntax amatch
+  (syntax-rules (else guard)
+    ((_ (op arg ...) cs ...)
+     (let ((v (op arg ...)))
+       (amatch v cs ...)))
+    ((_ v) (if #f #f))
+    ((_ v (else e0 e ...)) (begin e0 e ...))
+    ((_ v (pat (guard g ...) e0 e ...) cs ...)
+     (let ((fk (lambda () (amatch v cs ...))))
+       (apat v pat
+             (if (and g ...) (begin e0 e ...) (fk))
+             (fk))))
+    ((_ v (pat e0 e ...) cs ...)
+     (let ((fk (lambda () (amatch v cs ...))))
+       (apat v pat (begin e0 e ...) (fk))))))
+
+(define-syntax apat
+  (syntax-rules (_ quote unquote)
+    ((_ v _ kt kf) kt)
+    ((_ v () kt kf) (if (null? v) kt kf))
+    ((_ v (quote lit) kt kf)
+     (if (equal? v (quote lit)) kt kf))
+    ((_ v (unquote var) kt kf) (let ((var v)) kt))
+    ((_ v (x . y) kt kf)
+     (if (apair? v)
+         (let ((vx (acar v)) (vy (acdr v)))
+           (apat vx x (apat vy y kt kf) kf))
+         kf))
+    ((_ v lit kt kf) (if (eq? v (quote lit)) kt kf))))