Minor cleanup on BitArray constructors to fully allow for Integer types

[quinnj]

This came up from the following behavior on my 64-bit system:

julia> BitArray(Int64(10))
10-element BitArray{1}:
 false
 false
 false
 false
 false
 false
 false
 false
 false
 false

julia> BitArray(Int32(10))
ERROR: MethodError: `convert` has no method matching convert(::Type{BitArray{N}}, ::Int32)
This may have arisen from a call to the constructor BitArray{N}(...),
since type constructors fall back to convert methods.
Closest candidates are:
  call{T}(::Type{T}, ::Any)
  convert{T,N}(::Type{BitArray{N}}, ::AbstractArray{T,N})
  convert{T}(::Type{T}, ::T)
  ...
 in call at essentials.jl:56

julia> falses(Int64(10))
10-element BitArray{1}:
 false
 false
 false
 false
 false
 false
 false
 false
 false
 false

julia> falses(Int32(10))
ERROR: MethodError: `convert` has no method matching convert(::Type{BitArray{N}}, ::Int32)
This may have arisen from a call to the constructor BitArray{N}(...),
since type constructors fall back to convert methods.
Closest candidates are:
  call{T}(::Type{T}, ::Any)
  convert{T,N}(::Type{BitArray{N}}, ::AbstractArray{T,N})
  convert{T}(::Type{T}, ::T)
  ...
 in call at essentials.jl:56
 in falses at bitarray.jl:238

CC: @carlobaldassi

[tkelman]

wrong conflict resolution with #16498

[quinnj]

ah, I must have started editing this before pulling from master.

[tkelman]

appveyor's getting confused about mergability again...

[martinholters]

You could use convert(Dims, dims) instead of map(Int,dims). IMHO the intention is clearer that way, and IIUC, the code generated when all entries in dims are already Int is also more efficient.

[carlobaldassi]

LGTM. As far as I can tell from comparing the outputs of @code_llvm BitArray(10,10), the compiler is able to infer that map(Int,dims) is a no-op when dims is already Int.

[quinnj]

Thanks for taking a look @carlobaldassi.

[carlobaldassi]

Should probably be backported, too.

[tkelman]

Standard caveat that if you rely on this working, be careful about patch version in REQUIRE when a release with the backport is available.