Merge branch with instantiate.*

The following steps allow us to keep the history of both execute.* and instantiate.*:
1. In branch1 rename execute.* -> instantiate.* (git's history will consider instantiate to be the continuation of execute)
2. In branch1 remove execution code from instantiate.*
3. In branch2 rename instantiation code from execute.*
4. Merge branch1 into branch2.

lib/fizzy/CMakeLists.txt

@@ -13,6 +13,8 @@ target_sources(
     exceptions.hpp
     execute.cpp
     execute.hpp
+    instantiate.cpp
+    instantiate.hpp
     instructions.cpp
     instructions.hpp
     leb128.hpp