Print stack trace before instruction executes

[lrettig]

Per @cdetrio:

stack pointer starting at -32 https://github.com/ewasm/evm2wasm/blob/master/index.js#L509

this whole thing needs to be moved up, because the trace should print before the instruction executes (standardized trace). where it is now, it prints after the first instruction https://github.com/ewasm/evm2wasm/blob/master/index.js#L319-L322

Cf. ewasm/hera#164