Running spec test suite

[gumb0]

Spec test suite: https://github.com/WebAssembly/spec/tree/master/test/core

Converting *.wast files with a wast2json tool produces wasm files + json files like these:
https://gist.github.com/gumb0/a826ed24a6f16e5a6e88c7a9a88a8b3b
https://gist.github.com/gumb0/f7f3e443ced081fd1902c67881d0ac31

Basically for each command in json file we need to do one of the following:

• module - instantiate module from file (it is then used in the following commands)
  • when instantiate failed, skip following tests
  • provide imports to instantiate when required (link exports of registered modules)
  • spectest module provided by test harness for importing in tests
• register - register module to be used in the following commands for linking exports-imports of several modules (used in linking.wast, imports.wast, elem.wast)
• actions
  • invoke an exported function (by name)
  • get exported global value (by name)
  • choosing module for action by name (many cases in linking.json)
• assertions - check result of an action or module instantiation
  • assert_return
    • support case when no returned value expected (see break-drop.wast)
  • assert_trap
  • assert_exhaustion
  • assert_malformed (support needed only for "module_type": "binary")
  • assert_invalid
  • assert_unlinkable
  • assert_uninstantiable (in start.json and linking.json; in original wast it's assert_trap with module inside)
• action without assert (see memory_redundancy.wast)

The spec for all possible asserts/actions/commands is at https://github.com/WebAssembly/spec/tree/master/interpreter#scripts
(all of the assertions mentioned there are used in test suite)