Add some missing configuration flags (#227)

[bobappleyard]

By my reckoning, the following configuration flags were missing as of today:

wasmtime_config_wasm_tail_call_set
wasmtime_config_wasm_function_references_set
wasmtime_config_wasm_gc_set
wasmtime_config_wasm_wide_arithmetic_set
wasmtime_config_parallel_compilation_set
wasmtime_config_cranelift_nan_canonicalization_set
wasmtime_config_static_memory_forced_set
wasmtime_config_native_unwind_info_set
wasmtime_config_macos_use_mach_ports_set
wasmtime_config_memory_init_cow_set
wasmtime_config_async_support_set

With the exception of wasmtime_config_async_support_set, these flags are now included and should be settable.

It looks like wasmtime_config_async_support_set has a load of other settings that are needed in order to get it to work, so I'm skipping that one. Given how Go works, that would require a lot of thought, and I have taken a very mechanical approach here.

[alexcrichton]

Thanks for this!

[alexcrichton]

Thanks!