A first baby-step towards embedded builtins on ia32. This adds the
initial implementation for indirect load functionality (they still
depend on embedded external references to get the roots pointer).

External reference operands still directly embed external references.
We can change these sites to be root-relative once the root register
exists.

Drive-by: replace raw jmp(HeapObject), call(HeapObject),
mov(HeapObject) uses by their macro-assembler counterparts and add
sanity-checks to ensure we're not calling them by accident when
generating isolate-independent code.

Bug: v8:6666
Change-Id: Ide11273721bcdaaee06934eedeca9f39346d1d50
Reviewed-on: https://chromium-review.googlesource.com/1170687
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55332}