Fix issue #95: fix_includes.py now preserves line endings
If a file has mixed line endings or line endings can't be decided,
use Unix line endings.
Patch by André Stein.

git-svn-id: http://include-what-you-use.googlecode.com/svn/trunk@460 812d1f90-f944-d88a-411a-122bdc93e1ea