brewkit.rb changes ENV destructively, so lets not do that everytime a formula
is required. Now it's possible for other tools to require a formula
description without worrying about side-effects.
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.
