CommitDlg: UTF-8 chars in MERGE_MSG or SQUASH_MSG were not decoded correctly

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
TortoiseGitMerge: Add Search Up direction

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
Can search previous within the same line

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>