Added a writeFormat() method to Algorithm which must be called by the
write() method of derived classes.

used BufferPool mechanism instead

* remove overloads with explicit buffer, now BufferPool is used
* added async versions for all reduce functions

use correct types for integral/sum outputs

Without limits included, several CUDA related files fail to compile with
GCC on Ubuntu:

modules/cudaimgproc/src/hough_lines.cpp:136:9: error: ‘numeric_limits’ is not a member of ‘std’

Conflicts:
	modules/core/include/opencv2/core/cuda.hpp
	modules/cudacodec/src/thread.cpp
	modules/cudacodec/src/thread.hpp
	modules/superres/perf/perf_superres.cpp
	modules/superres/src/btv_l1_cuda.cpp
	modules/superres/src/optical_flow.cpp
	modules/videostab/src/global_motion.cpp
	modules/videostab/src/inpainting.cpp
	samples/cpp/stitching_detailed.cpp
	samples/cpp/videostab.cpp
	samples/gpu/stereo_multi.cpp