1. Add a new API -- sbgemv to support bfloat16 based gemv
2. Implement a generic kernel for sbgemv
3. Implement an avx512-bf16 based kernel for sbgemv

Signed-off-by: Chen, Guobing <guobing.chen@intel.com>

* Add an ARMV7 iOS build on Travis

* thread_local appears to be unavailable on ARMV7 iOS

* Add no-thumb option for ARMV7 IOS build to get it to accept DMB ISH

* Make local labels in macros of nrm2_vfpv3.S compatible with the xcode assembler

This is similar to fixes in gh-1929, but there was one remaining
occurance of this type of pattern in the driver/level2/*_thread.c
files.

same bug as seen in #1388, somehow missed in corresponding PR #1389

fixes #1748 as that half of the fix for #1332 appears to have been an overreaction on my part.

fixes #1872

otherwise the introduction of a static array in 8e5a108 to improve #532 breaks concurrent calls from multiple threads as seen in #1844

Address few more warnings

* Calculation of chunk range limits was ignoring num_cpu

bug introduced by me in #1262 - should fix #1388

* Calculation of range limits was ignoring num_cpu

bug introduced by me in #1262

* Calculation of chunk range limits was ignoring num_cpu

bug introduced by me in #1262

* Calculation of chunk range limits was ignoring num_cpu

bug introduced by me in #1262

* Calculation of chunk range limits was ignoring num_cpu

bug introduced by me in #1262

* Calculation of chunk range limits was ignoring num_cpu

bug introduced by me in #1262

* dead increments in driver/level2

* dead increments in kernel/generic

* part dead increments in kernel/x86_64