Hydrogen: fix keyed loads with string keys

Keyed loads should not unconditionally be compiled to element loads. Update KeyedLoadICs to keep track of the key type, so that Hydrogen can emit ICs for string-keyed loads it doesn't have inline support for.

BUG=v8:3167
R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/755513003

Cr-Commit-Position: refs/heads/master@{#25817}
[turbofan] Relax effects and context for JSToNumber(x:plain-primitive).

TEST=unittests
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/799413002

Cr-Commit-Position: refs/heads/master@{#25818}
Reland Call DisableInlineAllocation() in heap setup when flag inline_new is off.

BUG=

Review URL: https://codereview.chromium.org/806783002

Cr-Commit-Position: refs/heads/master@{#25819}
Take the build level into account for the version hash

build is the third number of the V8 version, and very likely to change
(in contrast to the patch level which typically is zero on canaries).

BUG=chromium:440984
R=mvstanton@chromium.org,yangguo@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/802363002

Cr-Commit-Position: refs/heads/master@{#25820}