Implement socket-api `recvmsg()` and `sendmsg()` for wasm app,
add sample and update document.

Fix the potential integer overflow of const index in const space of fast interpreter,
emit i32/i64.const opcode when the const index is larger than INT32_MAX.
And add check for the function local cell num.

During debugging, the debug client may request to malloc a memory space
to evaluate the user expressions. If we malloc memory from the linear memory,
it may fail when the thread is in stop status. We preserve a buffer during
creating debug instance, and use a simple bump pointer allocator to serve lldb's
memory request.

* check fast interpreter offset overflow

Fix args_get and environ_get issues in libc-wasi and libc-uvwasi implementation.

Use snprintf to format the string and then output it,
so as to support more formats and reduce the footprint.