add man files; add mod hash checking; add text decoding for blob

scripts/engine.cm

@@ -276,6 +276,14 @@ function deepFreeze(object) {
 globalThis.stone = deepFreeze
 stone.p = function(object)
 {
+  if (object instanceof blob) {
+    try {
+      object.read_logical(0)
+      return true
+    } catch(e) {
+      return false
+    }
+  }
   return Object.isFrozen(object) 
 }