merged to_index and indices into to_index
restrict some checkbounds signatures

A signature such as checkbounds(A::AbstractMatrix, I, J) was always
superseded by checkbounds(A::AbstractArray, I::Union(Real,AbstractArray)...)
simplify some checkbounds code

(also remove TODO: issue #1030 was closed)
bitarray: full multidimensional bounds checks

Fix #2495
Merge pull request #4663 from JuliaLang/cb/bitcheckbounds

Complete multidimensional bounds checks for BitArrays and more