fixed crash in cornersubpix.cpp/samplers.cpp (Bugfix #3402)

cvFindCornerSubpix is able to generate corner position updates far away from the image (if the determinant of the corner patch is very small).
This leads to large positive numbers which lead to integer wrap arounds (negative values) when win_size is added. This results in access errors in samplers.cpp (i.e. invalid memory accesses and thus crashes).
E.g. modules/imgproc/src/samplers.cpp:167
if( 0 <= ip.x && ip.x + win_size.width < src_size.width && \
Let's say ip.x is INT_MAX-5 (read: HUGE), and win_size.width is 6.
--> first check passes (ip.x is positive)
--> second check passes, as INT_MAX-5+6 = INT_MIN

gcc 4.7.1, 64bit Alces HPC Linux