Fix to fp32atan2 in certain special cases
Stuart Swales authored
Detail:
  fp32atan2 would give wrong results for special cases. For all of these
  the sign of x was copied onto the result (rather than the sign of y as
  intended); where both were ±INF a register with unknown value was used
  to determine whether to add ±pi/2.

Version 0.18. Tagged as 'VFPSupport-0_18'
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