基于STL string的高精度计算

支持以string类为存放格式的整数的多精度运算（包括+、-、*、/(整除)、％(取余)、-(取负)、乘方、开平方），部分允许string式的“整型”与int型混合运算，支持正负号，结果一律用string 型存放（多精度对单精度取余(用int)除外！）-Based on STL string of high-precision calculation of support for string-type format for storing the multi-precision integer operations (including 2B !,-,*,/( divisible), (remainder),- (negative check), involution, the square), and some allow the string-type　integer　and the int-type hybrid operation, to support the sign, the result will be stored using string-based (multi-to single-precision accuracy remainder (using int) except!)