[tests] Add host-byteorder-*-endian; update XFAILs of big-endian triples

Summary:
Triple components in `XFAIL` lines are tested against the target triple.
Various tests that are expected to fail on big-endian hosts are marked
as being `XFAIL` for big-endian targets. This patch corrects these tests
by having them test against a new `host-byteorder-big-endian` feature.

Reviewers: xingxue, sfertile, jasonliu

Reviewed By: xingxue

Subscribers: jvesely, nhaehnle, fedor.sergeev, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60551

llvm-svn: 359689