Create new menu id for "Abort Merge"

Signed-off-by: YueLinHo <b8732003@student.nsysu.edu.tw>

(Fixes issue #2035)

Signed-off-by: YueLinHo <b8732003@student.nsysu.edu.tw>
Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>
TortoiseGitMerge: Fix a maximizing problem maximizing on a non-primary monitor

Based on TortoiseSVN revision 25046, 25047

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