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
Rename copy_unsafe! to unsafe_copy! and export it (#2871).

Also add a version of unsafe_copy! that works with pointers,
and acts as a memcpy wrapper.

I have not added this to the list of deprecations since the function
was not exported until now.
Fix typo: export unsafe_copy!
Merge remote-tracking branch 'upstream/master'