Added new Intel-optimized 3x3 and 5x5 kernels to medianFilter.cl file and corresponding code to host in smooth.cpp

Only Intel platform and 1 channel images are supported.
Moved new kernels under conditional compilation to disable their build for 3-channel images; added condition to use new kernels only for images that are big enough
Adding explicit variable conversion in ocl_medianFilter() to suppress build errors on Linux & Mac
optimized cv::normalize in case of mask
Added condition to use optimized kernels for images of size that multiple of 4 only
Merge pull request #2794 from mletavin:pullreq/140516-median
Merge pull request #2808 from ilya-lavrenov:tapi_normalize_mask
ENH: Add more patterns to .gitignore

Update the .gitignore to ignore common
files that may accidently show up in the
source tree.
COMP: Fix problem with narrowing in c++11

modules/core/src/arithm.cpp:345:51:
error: constant expression evaluates to 4294967295 which cannot be narrowed to type 'int' [-Wc++11-narrowing]
static int CV_DECL_ALIGNED(16) v64f_absmask[] = { 0xffffffff, 0x7fffffff, 0xffffffff, 0x7fffffff };
                                                  ^~~~~~~~~~

Converted to unsigned int.  This variable is only used to initialize a bit pattern anywhy for a 128bit type.