TortoiseGitMerge: Accept more patch files

This patch enables TGitMerge to accept patches which are created using the *nix diff tool.

Signed-off-by: Sven Strickroth <email@cs-ware.de>
TortoiseGitMerge: Avoid "dupe" insertions on patching

Signed-off-by: Sven Strickroth <email@cs-ware.de>