Tag RelocInfo which belongs to native wasm code, and fix printing to
not try to access the Code object for CODE_TARGET, but rather just
print "(wasm trampoline)".

Bug: chromium:801785

R=mstarzinger@chromium.org

Change-Id: I84a37f0c48ed7397cccf677b4d0f0352e5aceb9d
Reviewed-on: https://chromium-review.googlesource.com/875271Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50758}