Refactor symbol table creation in binary writer (#1535)
Refactor symbol table creation in binary writer (#1535)

This commit refactors the representations of symbols in the binary
writer.  It will allow us to fix #1534 in a followup.
WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt,WebAssembly/sexpr-wasm-prototype,WebAssembly/sexpr-wasm-prototype,WebAssembly/wabt