Moving child function declaration instantiation to bytecode.

Moving child function declaration instantiation to bytecode.

Children functions need to be hoisted and instantiated at the beginning
of a function call. Previously, it was done as a part of C code
that implements JS function call.

Now, each child function is instantiated by FUNCTION instruction at a
function prelude. This makes global and function code similar, which in
turn allows to get rid of FUNCTION COPY instruction which was only
needed for global code.