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

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

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

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# gpg:                using RSA key 7A481E78868B4DB6A85A05C064DF38E8AF7E215F
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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 <[email protected]>