estimateSqrt32
zSig = estimateSqrt32( aExp, aSig ) + 2;
zSig0 = ( estimateSqrt32( aExp, term0 )>>1 ) + 1;
zSig = estimateSqrt32( aExp, aSig ) + 2;
zSig = estimateSqrt32( aExp, aSig>>21 );
zSig0 = estimateSqrt32( aExp, aSig0>>32 );
zSig0 = estimateSqrt32( aExp, aSig0>>17 );