 Avoid unexpected line breaks in version_string.inc
 Avoid unexpected line breaks in version_string.inc

The Android NDK 16b has a bug that sets the ANDROID_NDK_REVISION
variable incorrectly, generating an unexpected line break in the
middle of the string. This breaks the build as the generated
version_string.inc presents an invalid C string.

Remove leading and trailing line breaks, warns for line breaks in the
middle of 'msg' and escape them before appending to
OPENCV_BUILD_INFO_STR.

opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv