gitk: Do not depend on Cygwin's "kill" command on Windows
gitk: Do not depend on Cygwin's "kill" command on Windows

Windows does not necessarily mean Cygwin, it could also be MSYS. The
latter ships with a version of "kill" that does not understand "-f".
In msysgit this was addressed by shipping Cygwin's version of kill.

Properly fix this by using the stock Windows "taskkill" command instead,
which is available since Windows XP Professional.

Signed-off-by: Sebastian Schuberth <77397652b38ec60b50e56236b813774ce842bcdf@gmail.com>
Signed-off-by: Paul Mackerras <19a0ba370c443ba08d20b5061586430ab449ee8c@samba.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git