edify extensions for OTA package installation, part 1

Adds the following edify functions:

  mount unmount format show_progress delete delete_recursive
  package_extract symlink set_perm set_perm_recursive

This set is enough to extract and install the system part of a (full)
OTA package.

Adds the updater binary that extracts an edify script from the OTA
package and then executes it.  Minor changes to the edify core (adds a
sleep() builtin for debugging, adds "." to the set of characters that
can appear in an unquoted string).
diff --git a/edify/main.c b/edify/main.c
index 4d65da2..c959683 100644
--- a/edify/main.c
+++ b/edify/main.c
@@ -158,7 +158,14 @@
   printf("parse returned %d\n", error);
   if (error == 0) {
     char* result = Evaluate(NULL, root);
-    printf("result is [%s]\n", result == NULL ? "(NULL)" : result);
+    if (result == NULL) {
+      char* errmsg = GetError();
+      printf("result was NULL, message is: %s\n",
+             (errmsg == NULL ? "(NULL)" : errmsg));
+      ClearError();
+    } else {
+      printf("result is [%s]\n", result);
+    }
   }
   return 0;
 }