provide a NEON version of arm/sgemm #2632

Job	Run time
xbuild-x86_64	9m 52s
xbuild-ios32	5m 18s
xbuild-ios	6m 10s
build-windows (make, gfortran, 0, 1)	7m 19s
build-windows (cmake, gfortran, 0, 0)	12m 38s
build-windows (make, gfortran, 0, 0)	7m 2s
build-windows (cmake, gfortran, 1, 1)	16m 12s
build-windows (cmake, gfortran, 0, 1)	18m 3s
build-windows (cmake, gfortran, 1, 0)	34m 18s
build-windows (make, gfortran, 1, 1)	7m 3s
build-windows (make, gfortran, 1, 0)	8m 28s
	2h 12m 23s

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