Import GMP and MPFR

GMP is a multi precision library which provides bigint and rational, MPFR is also  multi precision library which provides bigfloat that is natural extension of IEEE 754.
Both are licensed LGPL.

This patch introduces
  + acculate number types of bigint, rational and bigfloat.
  + #e #i #b #o #d #x reader
  + number<->string in which you can specify radix

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