Convert files to unix-style EOL before hash check

On Windows bootstrap files could have windows-style EOL depending on the
core.autocrlf git setting.
Fix 1ecad35033429dbf39cca7bc7421780cbf95f3ec

file(COPY) requires a directory and not a file name
Fix comment
IncludeUrl: Support non-native end-of-line styles

Do not fail download if file is remote and hash mismatches. This could
be caused by different end of line style.
Instead download it and perform the hast test later with the files, and
the files switched to the non-native end-of-line style.
AddUninstallTarget: Use the uppercase convention for target name on MSVC and XCode
Add FIXME comment
Check on CMAKE_GENERATOR instead of MSVC_VERSION OR XCODE_VERSION

The old check for some reason does not work every time
AddUninstallTarget: Use CMakePredefinedTargets folder when USE_FOLDERS is enabled
Enable USE_FOLDERS global property
Improve AppVeyor script
AppVeyor test