+ for strings, global js object, new Foo() works

* module/language/ecmascript/array.scm (*array-prototype*): Declare the
  constructor.

* module/language/ecmascript/base.scm (pput, pdel): Remove some needless
  checks.
  (new): Move definition of new here, and use the constructor.

* module/language/ecmascript/compile-ghil.scm (compile-ghil): Add a stub
  so that when we load a compiled JS program, we make sure the runtime
  has been booted.

* module/language/ecmascript/function.scm (js-constructor): Export a
  js-constructor method instead of a new method.

* module/language/ecmascript/impl.scm (<js-global-object>): Define a new
  class for the global "this" object, wrapping bindings from the current
  module.
  (init-js-bindings!): Define the dozen or so global properties, in the
  current module.
  (+): Define addition operations for non-numbers. This is efficient
  because the generics are only dispatched if the fast-path fails.

module/language/ecmascript/impl.scm

@@ -28,7 +28,7 @@
                pget pput pdel has-property?
                ->boolean
                new-object new new-array)
-  #:export (get-this
+  #:export (js-init get-this
             typeof
             bitwise-not logical-not
             shift
@@ -36,6 +36,44 @@
             band bxor bior))
 
 
+(define-class <js-global-object> (<js-object>))
+(define-method (pget (o <js-global-object>) (p <string>))
+  (pget o (string->symbol p)))
+(define-method (pget (o <js-global-object>) (p <symbol>))
+  (let ((v (module-variable (current-module) p)))
+    (if v
+        (variable-ref v)
+        (next-method))))
+(define-method (pput (o <js-global-object>) (p <string>) v)
+  (pput o (string->symbol p) v))
+(define-method (pput (o <js-global-object>) (p <symbol>) v)
+  (module-define! (current-module) p v))
+(define-method (prop-attrs (o <js-global-object>) (p <symbol>))
+  (cond ((module-local-variable (current-module) p)
+         '())
+        ((module-variable (current-module) p)
+         '(DontDelete ReadOnly))
+        (else (next-method))))
+(define-method (prop-attrs (o <js-global-object>) (p <string>))
+  (prop-attrs o (string->symbol p)))
+
+(define (init-js-bindings! mod)
+  (module-define! mod 'NaN +nan.0)
+  (module-define! mod 'Infinity +inf.0)
+  (module-define! mod 'undefined *undefined*)
+  ;; isNAN, isFinite, parseFloat, parseInt, eval
+  ;; decodeURI, decodeURIComponent, encodeURI, encodeURIComponent
+  ;; Object Function Array String Boolean Number Date RegExp Error EvalError
+  ;; RangeError ReferenceError SyntaxError TypeError URIError
+  (module-define! mod 'Object *object-prototype*)
+  (module-define! mod 'Array *array-prototype*))
+
+(define (js-init)
+  (cond ((get-this))
+        (else
+         (fluid-set! *this* (make <js-global-object>))
+         (init-js-bindings! (current-module)))))
+
 (define (get-this)
   (fluid-ref *this*))
 
@@ -60,3 +98,15 @@
 (define bior logior)
 
 (define mod modulo)
+
+(define-method (+ (a <string>) (b <string>))
+  (string-append a b))
+
+(define-method (+ (a <string>) b)
+  (string-append a (->string b)))
+
+(define-method (+ a (b <string>))
+  (string-append (->string a) b))
+
+(define-method (+ a b)
+  (+ (->number a) (->number b)))