Move stdlib to common

[winksaville]

You referred to it as stdlib, should it be in a dir called stdlib?

[MaxGraey]

It's need to move forward and exclude runtime.js and wrapper.js from library.

[winksaville]

I corrected my previous statement, so maybe you misunderstood. I'm suggesting rather than being called common the directory should be called stdlib?

[nidin]

@winksaville we will refactor stdlib later, now "common" contains common library source code for asm.js and WASM.

[winksaville]

SG