Mac OS X 10.7 and newer don't come with Java installed. They do
include some stub binaries, which ask the user if they want to
install Java when run.

OpenCV's cmake script just checks for the existence of an ant
binary and assumes that Java's available if ant is. As a result,
cmake will configure the build to use Java and it will fail once
it tries to compile the Java bindings.

This fixes the issue by checking for the exit status of
`ant -version` - it exits 0 if Java is installed, or 1
otherwise.(cherry picked from commit a423afdd)

Remove weirdo unicode – and just use a normal -(cherry picked from commit 0d49de51)

initial optical flow was not cleaned during the second call

The generated OpenCV Java source can contain characters outside of ASCII on some systems – this patch allows the ant task to compile them.
(cherry picked from commit f3ee55e0)