fix #4163, remove xdump and simplify dump

[JeffBezanson]

This replaces these functions with a single one that just shows everything inside an object.
Some examples:

julia> dump(("a",1+2im))
Tuple{ASCIIString,Complex{Int64}}
  1: ASCIIString
    data: Array(UInt8,(1,)) UInt8[0x61]
  2: Complex{Int64}
    re: Int64 1
    im: Int64 2

julia> dump(methods(sin).defs.func)
LambdaInfo
  code: Array(UInt8,(67,)) UInt8[0x10,0x88,0x88,0xcf,0x0e,0x10,0xb9,0x02,0x0a,0x66  …  0x1d,0x16,0x15,0x3b,0x0e,0x10,0x00,0x07,0x88,0x1d]
  slotnames: Array(Any,(2,))
    1: Symbol #self#
    2: Symbol a
  slottypes: Void nothing
  slotflags: Array(UInt8,(2,)) UInt8[0x00,0x00]
  gensymtypes: Int64 0
  rettype: Any
  sparam_syms: empty SimpleVector
  sparam_vals: empty SimpleVector
  tfunc: Void nothing
  name: Symbol sin
  roots: #undef
  specTypes: #undef
  unspecialized: #undef
  specializations: #undef
  module: Module Base
  def: LambdaInfo
# much longer but I'll cut it off here

julia> dump(StridedArray)
TypeConstructor
  parameters: SimpleVector
    1: TypeVar
      name: Symbol T
      lb: Union{}
      ub: Any
      bound: Bool false
    2: TypeVar
      name: Symbol N
      lb: Union{}
      ub: Any
      bound: Bool false
    3: TypeVar
      name: Symbol A
      lb: Union{}
      ub: DenseArray{T,N} <: AbstractArray{T,N}
      bound: Bool false
    4: TypeVar
      name: Symbol I
      lb: Union{}
      ub: Tuple{Vararg{Union{Base.AbstractCartesianIndex{N},Base.NoSlice,Colon,Int64,Range{Int64}}}} <: Any
      bound: Bool false
  body: Union{DenseArray{T,N},SubArray{T,N,A<:DenseArray{T,N},I<:Tuple{Vararg{Union{Base.AbstractCartesianIndex{N},Base.NoSlice,Colon,Int64,Range{Int64}}}},L}}

[vtjnash]

should probably always be 1:nfields(T), since the indices are unique and always available

[JeffBezanson]

One remaining issue is that dump was intended to be overloaded, and several packages do so. However I don't think this is a good idea; dump should show concrete structure, and all other printing can be handled by show at different verbosity levels.

[tshort]

So, dump becomes what xdump was. That seems like a loss of functionality for viewing contents of tree-like structures. Consider the following with the existing dump function:

julia> d = Dict(:a => 1, :b => Dict(:x => Dict(:y => [2,3], :z => 3)))
Dict{Symbol,Any} with 2 entries:
  :a => 1
  :b => Dict(:x=>Dict{Symbol,Any}(:y=>[2,3],:z=>3))

julia> dump(d)
Dict{Symbol,Any} len 2
  a: Int64 1
  b: Dict{Symbol,Dict{Symbol,Any}} len 1
    x: Dict{Symbol,Any} len 2
      y: Array(Int64,(2,)) [2,3]
      z: Int64 3

julia> show(d)
Dict{Symbol,Any}(:a=>1,:b=>Dict(:x=>Dict{Symbol,Any}(:y=>[2,3],:z=>3)))

If I follow this right, that output of dump will go away, and it'll show the internals of the dict. The current output is much more helpful than that printed by show. Can we have another function that does what dump does now?

[JeffBezanson]

That strikes me as just an aesthetic difference of opinion on how Dicts should be printed. I think it could be handled by verbosity levels in show. Actually the AbstractTrees package provides something like this, with much nicer output to boot.

[ivirshup]

Can this be merged?

[ivirshup]

Is anything not mentioned here stopping this from being merged?

If not, I'd be up for branching off this and fixing it up for a merge.

[JeffBezanson]

Basically just needs a rebase and a NEWS entry. I'll do that and merge.

[tkelman]

please run genstdlib and commit updates at the same time

[tkelman]

several places in docs need fixing

[ivirshup]

What else needs fixes past types.rst?

[tkelman]

base/show.jl:1040:                #    xdump(fn, io, fieldtype(x,idx), n - 1, string(indent, "  "))
contrib/BBEditTextWrangler-julia.plist:1219:            <string>xdump</string>
doc/devdocs/types.rst:93:   julia> xdump(Array)
doc/devdocs/types.rst:107:   julia> xdump(T)
doc/devdocs/types.rst:136:   xdump(tv)
doc/devdocs/types.rst:172:   julia> xdump(p1[1].parameters[1])
doc/devdocs/types.rst:179:   julia> xdump(p3[1].parameters[1])
doc/devdocs/types.rst:313:   julia> xdump(Array.name)
doc/stdlib/io-network.rst:516:.. function:: xdump(x)