Stubs for removed functions to make wasm environment compatible with old runtimes

[svyatonik]

Functions were removed in #4162 => current client is unable to sync Flaming Fir (but we can reset this chain) and at some point (when commit is picked into polkadot-master) will be unable to sync Kusama (we do not want to reset this chain, right?).

[svyatonik]

For reference, if you'll try to sync FF now (with empty db), you'll get:

2019-12-16 14:27:52 Substrate Node
2019-12-16 14:27:52   version 2.0.0-13b1308-x86_64-linux-gnu
2019-12-16 14:27:52   by Parity Technologies, 2017-2019
2019-12-16 14:27:52 Chain specification: Flaming Fir
2019-12-16 14:27:52 Node name: mountainous-fire-8140
2019-12-16 14:27:52 Roles: FULL
2019-12-16 14:27:53 Initializing Genesis block/state (state: 0xd733…e696, header-hash: 0xb653…1d25)
2019-12-16 14:27:53 Loading GRANDPA authority set from genesis on what appears to be first startup.
2019-12-16 14:27:54 cannot create a runtime: Instantiation("Instantiation: Export ext_get_allocated_child_storage not found")
Error: Service(Client(Execution(InvalidCode("Instantiation(\"Instantiation: Export ext_get_allocated_child_storage not found\")"))))

[expenses]

Fixed the in-browser light client for me! :D

[bkchr]

These functions are not used in Kusama anymore, so it is fine to delete them. And I would not like to bring them back. FF is dead anyway.

@ddorgan is currently setting up a new one. (A new test net)