LibWasm: Start implementing a naive bytecode interpreter

As the parser now flattens out the instructions and inserts synthetic
nesting/structured instructions where needed, we can treat the whole
thing as a simple parsed bytecode stream.
This currently knows how to execute the following instructions:
- unreachable
- nop
- local.get
- local.set
- {i,f}{32,64}.const
- block
- loop
- if/else
- branch / branch_if
- i32_add
- i32_and/or/xor
- i32_ne

This also extends the 'wasm' utility to optionally execute the first
function in the module with optionally user-supplied arguments.

Meta/CMake/all_the_debug_macros.cmake

@@ -179,6 +179,7 @@ set(LINE_EDITOR_DEBUG ON)
 set(LANGUAGE_SERVER_DEBUG ON)
 set(GL_DEBUG ON)
 set(WASM_BINPARSER_DEBUG ON)
+set(WASM_TRACE_DEBUG ON)
 set(PDF_DEBUG ON)
 set(SOLITAIRE_DEBUG ON)