tool_operate: Don't sanitize --output path (Windows)

Due to path separators being incorrectly sanitized in --output
pathnames, eg -o c:\foo => c__foo

This is a partial revert of 3017d8a8 until I write a proper fix. The
remote-name will continue to be sanitized, but if the user specified an
--output with string replacement (#1, #2, etc) that data is unsanitized
until I finish a fix.

Bug: https://github.com/bagder/curl/issues/624
Reported-by: Octavio Schroeder