OCaml bindings: fix attributes to use all 32 bits

OCaml's int is limited to 31 bits on 32-bit architectures, so use Int32
explicitly.
Also add an unpack_attr, and {function,param,instr}_attr functions to read
the attributes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@141996 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed