Use state machine externalities in validation runtime. (#214)

* test

* switch to branch

* Use modified.

* Use sp_externalities environmental primitives

* Change to latest no_std version, add missing host function boilerplate.

* remove comment (was used for debugging).

* fixes

* with_externalities factor

* Read merged change from overlay.

cumulus/Cargo.lock

@@ -1193,9 +1193,11 @@ dependencies = [
  "sp-blockchain",
  "sp-consensus",
  "sp-core",
+ "sp-externalities",
  "sp-io",
  "sp-keyring",
  "sp-runtime",
+ "sp-state-machine",
  "sp-std",
  "sp-trie",
  "trie-db",