Remove UNIX-based trap statements

These need to be replaced with more Windows-friendly
signal processing mechanism
Skip fix_etc_hosts on Windows
Use File::SEPARATOR when building TRAVIS_BUILD_DIR
Fix TRAVIS_BUILD_DIR on Windows

On Windows, we can't write
  $Env:TRAVIS_BUILD_DIR=$HOME/build/jruby/jruby

since the right hand side contains slashes.
It needs to be quoted, but this needs to happen only in certain
cases.
It should not happen on arbitrary cases, since user-defined
environment variables may contain quotation marks already.
Skip updating resolv.conf on Windows
Remove bash-only stuff from test data
Tweak Node to compile sensible PowerShell

With this change, it is possible to compile PowerShell script
containing if/elseif/else conditionals under some con
Fix up some logic involving conditionals.