Fix the following error for ocl::getOpenCLPlatforms() on Ubuntu 12.04 with gcc 4.8
OpenCV Error: Unknown error code -6 (OpenCL function is not available: [clGetPlatformIDs]) in opencl_check_fn, file /home/ahb/software/opencv/modules/ocl/src/cl_runtime/cl_runtime.cpp, line 83

The issue results from modules/ocl/src/cl_runtime/cl_runtime.cpp checking for
"linux" instead of "__linux__" (cp.  http://sourceforge.net/p/predef/wiki/OperatingSystems/)

Adjust all other occurrences of "defined(linux)" as well.
All installed files marked with component names for install customization.
Initial Linux packages build rools.
LICENSE added.
More accurate arch setup for deb and rpm packages.