Misc doc improvements (#28719)

* doc: remove unused file.

* doc: improve docstring of at-big_str

* doc: fix some broken links

(cherry picked from commit dbcc152)

base/int.jl

@@ -579,9 +579,18 @@ end
     @big_str str
     @big_str(str)
 
-`@big_str` parses a string into a BigInt
-Throws an `ArgumentError` if the string is not a valid integer
-Removes all underscores `_` from the string
+Parse a string into a [`BigInt`](@ref) or [`BigFloat`](@ref),
+and throw an `ArgumentError` if the string is not a valid number.
+For integers `_` is allowed in the string as a separator.
+
+# Examples
+```jldoctest
+julia> big"123_456"
+123456
+
+julia> big"7891.5"
+7.8915e+03
+```
 """
 macro big_str(s)
     if '_' in s

doc/src/base/numbers.md

@@ -89,8 +89,6 @@ Base.isinteger
 Base.isreal
 Core.Float32(::Any)
 Core.Float64(::Any)
-Base.GMP.BigInt(::Any)
-Base.MPFR.BigFloat(::Any)
 Base.Rounding.rounding
 Base.Rounding.setrounding(::Type, ::Any)
 Base.Rounding.setrounding(::Function, ::Type, ::RoundingMode)
@@ -113,18 +111,22 @@ Base.@int128_str
 Base.@uint128_str
 ```
 
-## BigFloats
+## BigFloats and BigInts
 
-The [`BigFloat`](@ref) type implements arbitrary-precision floating-point arithmetic using
-the [GNU MPFR library](http://www.mpfr.org/).
+The [`BigFloat`](@ref) and [`BigInt`](@ref) types implements
+arbitrary-precision floating point and integer arithmetic, respectively. For
+[`BigFloat`](@ref) the [GNU MPFR library](http://www.mpfr.org/) is used,
+and for [`BigInt`](@ref) the [GNU Multiple Precision Arithmetic Library (GMP)]
+(https://gmplib.org) is used.
 
 ```@docs
+Base.MPFR.BigFloat(::Any)
 Base.precision
 Base.MPFR.precision(::Type{BigFloat})
 Base.MPFR.setprecision
 Base.MPFR.BigFloat(x, prec::Int)
-BigFloat(x::Union{Integer, AbstractFloat, String}, rounding::RoundingMode)
+Base.MPFR.BigFloat(x::Union{Integer, AbstractFloat, String}, rounding::RoundingMode)
 Base.MPFR.BigFloat(x, prec::Int, rounding::RoundingMode)
-Base.MPFR.BigFloat(x::String)
+Base.GMP.BigInt(::Any)
 Base.@big_str
 ```