Moving BigFloat to stdlib?

With all the other things moving out of Base, there are not really many places where BigFloat is used anymore:

In int.jl, there is a parsing routine that would simply move to stdlib/BigFloat.jl
mpfr.jl would move to stdlib/BigFloat.jl
In printf.jl (which I’d thought had already moved to stdlib/Printf.jl), there is some code to print out BigFloats and BigInts.
There’s a single function in hashing2.jl, which also would just move to stdlib/BigFloat.jl.
There are a few lines in sysimg.jl:

using .MPFR
big(n::Integer) = convert(BigInt,n)
big(x::AbstractFloat) = convert(BigFloat,x)
big(q::Rational) = big(numerator(q))//big(denominator(q))

There’s a line in exports.jl.

The only real use is in irrationals.jl, and I believe the BigFloat part of irrationals could be moved also out.

This would remove a large dependency from Base (the MPFR library),
and allow BigFloats to be updated without waiting on the Julia timeline.