n5.1.8
arm: rename ARMVFP config symbol to VFP
Merge commit '41cf3e3b1ca375962951fde1b90a03b16197d205'
avutil/attributes: add AV_GCC_VERSION_AT_MOST
avutil: use getauxval(3) for CPU capabilities on linux/android ARM
Merge commit '4cf84e254ae75b524e1cacae499a97d7cc9e5906'
Merge commit '7ffda66fd5c81af4725bff7c2c4f207ba2aa0613'
Merge commit '831a1180785a786272cdcefb71566a770bfb879e'
Reinstate proper FFmpeg license for all files.
arm: Check for have_vfp_vm instead of !have_vfpv3 for float_dsp_vfp
armv6: Accelerate butterflies_float
libavutil: Add saturating subtraction functions
all: Add missing header guards
arm/aarch64: Use mach_absolute_time as timer on apple platforms