According to the ES2015 specification, bound functions are exotic
objects, and thus don't need to be implemented as JSFunctions. So
we introduce a new JSBoundFunction type to represent bound functions
and make them optimizable. This already improves the performance of
calling or constructing bound functions by 10-100x depending on the
use case because we avoid the crazy dance between JavaScript and C++
that was implemented in v8natives.js previously.

There's still room for improvement in the performance of actually
creating bound functions, which is also relevant in practice, but
we already have a plan how to accomplish that later.

The mips/mips64 ports were contributed by akos.palfi@imgtec.com.

CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_chromium_rel_ng;tryserver.blink:linux_blink_rel
BUG=chromium:535408, chromium:571299, v8:4629
LOG=n

Review URL: https://codereview.chromium.org/1542963002

Cr-Commit-Position: refs/heads/master@{#33042}