fix #2899, regression
rename BoundingBox contains() to isinside()
helpful error for contains(String, String)
speed up Matrix{Float64|Complex128}*vector, where the vector is of some smaller type. closes #2853

in such a case, it is reasonable to copy the vector to a different type.
make Nothing immutable
fix incorrect ccall signatures of memset, jl_readBuffer,
jl_uv_fs_t_ptr_offset, and memchr, as identified in #2901