Make TemplateLiteral hashing algorithm more memory efficient

Previously, a separate string to be hashed (in order to help determine the need to
use a cached Template Call Site) was built up by joining UTF8 spans within a template.

Now, the hash key is generated from the original spans, removing the need to allocate a new
buffer and copy bytes into it.

BUG=

Review URL: https://codereview.chromium.org/765473006

Cr-Commit-Position: refs/heads/master@{#25549}
Set @@toStringTag on GeneratorFunction prototype.

R=caitpotter88@gmail.com
BUG=v8:3502
LOG=N

Review URL: https://codereview.chromium.org/764823002

Cr-Commit-Position: refs/heads/master@{#25550}
[turbofan] Avoid repeatedly revisiting inputs in GraphReducer.

R=mstarzinger@chromium.org
BUG=

Review URL: https://codereview.chromium.org/753073009

Cr-Commit-Position: refs/heads/master@{#25551}
Flesh out vector ic state query and set mechanisms.

The IC system now fully integrates the vector concept and can
handle loads and keyed loads vector-based.

BUG=
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/754303003

Cr-Commit-Position: refs/heads/master@{#25552}
Set clang directory in gyp.

BUG=

Review URL: https://codereview.chromium.org/764803002

Cr-Commit-Position: refs/heads/master@{#25553}
MIPS: Flesh out vector ic state query and set mechanisms.

Port c142994f742b52cd59aa15d0961d4b0034bcbf88

Original commit message:
The IC system now fully integrates the vector concept and can
handle loads and keyed loads vector-based.

BUG=
R=akos.palfi@imgtec.com

Review URL: https://codereview.chromium.org/752553005

Patch from Balazs Kilvady <balazs.kilvady@imgtec.com>.

Cr-Commit-Position: refs/heads/master@{#25554}