Respect the mixing EOL when review patch with TortoiseGitMerge

The steps:
1. Invoke "Apply Patches" dialog
2. Add a patch with mixing CRLF(line 1) and LF(line 2)
3. Right click on that patch in list
4. Click Review Patch with TortoiseGitMerge
5. The EOL of Line 2 is CRLF (should be LF)

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>
Pass value of core.autocrlf to TortoiseGitMerge

Want to use the value of git config in TortoiseGitMerge,
but don't want to involve git source files into TortoiseGitMerge Project.

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>
Show "correct" EOL when core.autocrlf = false

"correct" means it is the same EOL between showing and clean working tree.

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>
Mixed EOL should be always Mixed EOL

Whatever the value of core.autocrlf is,
it is still mixed EOL in repository and working tree
after applying/committing the mixed EOL file.

Signed-off-by: Yue Lin Ho <b8732003@student.nsysu.edu.tw>