说明：  GMP 是一个任意精度的数学计算库。 想升级GCC到4.3.0版本,在安装前,需要先安装MPFR和GMP.
(GMP is a free library for arbitrary precision arithmetic, operating on signed integers, rational numbers, and floating point numbers. There is no practical limit to the precision except the ones implied by the available memory in the machine GMP runs on. GMP has a rich set of functions, and the functions have a regular interface. )