- properly detect Android SDK support of Ant/Gradle projects
- divide processing of And/Gradle based projects

- Recommended compiler checks:
  - GCC: CV_GCC
  - Clang: CV_CLANG
- fixed problem with CMAKE_CXX_COMPILER_ID=Clang/AppleClang mess on MacOSX
  Details: cmake --help-policy CMP0025
- do not declare Clang as GCC compiler

* cmake: add ocv_get_smart_file_name() macro

* cmake: avoid adding files for unavailable dispatch modes

Documentation generation refactoring (#10621)

* Documentation build updates:

- disable documentation by default, do not add to ALL target
- combine Doxygen and Javadoc
- optimize Doxygen html

* javadoc: fix path in build directory

* cmake: fix "Documentation" status line

fixes CUDA build

CUDA implementation wants to convert std::vector<KeyPoint> <-> GpuMat.
There is no direct mapping from KeyPoint (mix of int/float fields)
into cv::Mat element type, so this conversion must be avoided.

Legacy mode is turned back for CUDA builds.