Properly handle known JSBoundFunction instances as targets to
JSConstruct by inlining the construction of the eventual target.
Also if the target is the result of a JSCreateBoundFunction call,
where we can also fold the construction and construct the bound
target function directly instead.

This addresses half of the TODO in the JSConstruct lowering in the
JSCallReducer where so far we didn't handle bound functions.

Bug: v8:5267, v8:7109
Change-Id: I022dc7d4fbbe2c9972472e78a6d64f51e3134c94
Reviewed-on: https://chromium-review.googlesource.com/792947Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49664}