Whitespace.
ARMAsmBackend.cpp: Use Triple::isOSBinFormatCOFF() instead of isOSWindows().

FYI, isOSBinFormatCOFF() is as same as isOSWindows(), on trunk.
Tweak a couple of tests on win32 hosts with +Asserts.

  - Don't use assert(0), or tests may pass or fail according to assertions.
  - For now, The tests are marked as XFAIL for win32 hosts.

FIXME: Could we avoid XFAIL to specify triple in the RUN lines?