When SSE is enabled, the compilation fails with VS2015

When including cl.hpp, we have the following errors:

CL/cl.hpp(6044): error C2719: 'fillColor': formal parameter with requested alignment of 16 won't be aligned
CL/cl.hpp(6078): error C2719: 'fillColor': formal parameter with requested alignment of 16 won't be aligned

These, I think, are linked to the type cl_int4 which is a union that contains `__cl_int4 v4;` when `__CL_INT4__` is defined, itself defined if `__SSE2__` is defined.
I guess that `__m128i` variables must be aligned, which cannot be done in function parameters on VS.

The workaround that we use is to change the fillcolor parameter from a `cl_int4` to a `const cl_int4&`. Then it compiles fine.

Start in cl.hpp around lines 6044 and 6078, where fillColor is passed as cl_int4, and compare the __cl_int4/__m128i alignment path enabled by __SSE2__. Verify the parameter handling by compiling with SSE enabled under VS2015 and confirming both reported errors disappear.

Written by the indexing model from the issue text.