[0xC] Convert to stack machine semantics.
[0xC] Use section codes instead of names.
[0xC] Add elements section decoding.
[0xC] Decoding of globals section.
[0xC] Decoding of memory section.
[0xC] Decoding of imports section.
[0xC] Decoding of exports section.
[0xC] Decoding of data section.
[0xC] Remove CallImport bytecode.
[0xC] Function bodies have an implicit block.
[0xC] Remove the bottom label from loops.
[0xC] Add signatures to blocks.
[0xC] Remove arities from branches.
Add tests for init expression decoding.
Rework compilation of import wrappers and how they are patched.
Rework function indices in debugging.
Fix ASM->WASM builder for stack machine.
Reorganize asm.js foreign functions due to import indices change.

R=ahaas@chromium.org,rossberg@chromium.org,bradnelson@chromium.org
BUG=chromium:575167
LOG=Y

Review-Url: https://codereview.chromium.org/2345593003
Cr-Commit-Position: refs/heads/master@{#39678}