Issue Description

As mentioned in previous issues (#1428, #1443, #1464, #1484), there have been issues executing AVX instructions on CPUs that don't support AVX (causing SIGILL, "Illegal instruction (core dumped)"). Using SDK version 2.14.1, the issue is two-fold:

1. If I compile with -mavx, my application crashes at global initialization. I see that there is auto-selection code to bypass the AVX implementation if not supported on a CPU, but in debugging, I saw crashes in two different locations (one in librealsense and one in another library). Generally speaking, adding -mavx gives the compiler free-reign to optimize using AVX wherever it wishes, so I don't think this should always be enabled for all non-ARM builds.

2. If I remove -mavx, the build fails due to SSSE3 guards (which my processor supports) where AVX guards should be used instead. I have a patch for this, which is ultimately the solution to my issue. I'll send a pull request with this patch shortly.