Bit-burst algorithm version of BigMath.erf and BigMath.erfc

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Implement Bit-burst algorithm version of BigMath.erf and BigMath.erfc

Bit-burst algorithm implementation

Repeatedly apply Taylor expansion at increasing x.

1. Split x into x0 + x1 + x2 + ...
2. Calculate f(x0) by Taylor expansion(erf) or asymptotic expansion(erfc)
3. Calculate f(x0 + x1) by Taylor expansion of f at x0
4. Calculate f(x0 + x1 + x2) by Taylor expansion of f at x0 + x1
5. So on...

Each Taylor expansion calculation uses binary-splitting method.
Details are described in source code comment.

Benchmark

# Erf of integerBigMath.erf(10,10000)# processing time: 0.324237s → 0.094490sBigMath.erf(10,100000)# processing time: 13.380194s → 1.044322s# Erf of full-precision numberBigMath.erf(BigDecimal(2).sqrt(10000),10000)# processing time: 0.501813s → 0.268420sBigMath.erf(BigDecimal(2).sqrt(100000),100000)# processing time: 21.532002s → 5.708505s# Erfc of integerBigMath.erfc(1234,10000)# processing time: 0.216168s → 0.094400sBigMath.erfc(1234,100000)# processing time: 19.402288s → 1.258311s# Erfc of full-precision numberBigMath.erfc(1234 + BigDecimal(4).div(7,10000),10000)# processing time: 4.616296s → 0.219974sBigMath.erfc(1234 + BigDecimal(4).div(7,20000),20000)# processing time: 23.335180s → 0.572202sBigMath.erfc(1234 + BigDecimal(4).div(7,100000),100000)# processing time: 1137.080714s → 5.270239s