Merge remote-tracking branch 'remotes/rth/tags/pull-sf-20200829' into staging

* float16 comparison wrappers
* float16 conversions to/from 8-bit integers
* bfloat16 support

# gpg: Signature made Sun 30 Aug 2020 03:29:54 BST
# gpg:                using RSA key 7A481E78868B4DB6A85A05C064DF38E8AF7E215F
# gpg:                issuer "richard.henderson@linaro.org"
# gpg: Good signature from "Richard Henderson <richard.henderson@linaro.org>" [full]
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* remotes/rth/tags/pull-sf-20200829:
  softfloat: Define comparison operations for bfloat16
  softfloat: Define misc operations for bfloat16
  softfloat: Define convert operations for bfloat16
  softfloat: Define operations for bfloat16
  softfloat: Add float16_is_normal
  softfloat: Add fp16 and uint8/int8 conversion functions
  softfloat: Implement the full set of comparisons for float16

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>