Check in some old changes to the binding, from before I had commit access. - Add bindings for InsertValue and ExtractValue - Updates to use new APIs where they were renamed or removed. - Add generic error messages if LLVM didn't provide one. - Enable typesafe variadic arguments for GetGEP.

enum
{
    LLVMnone,
    LLVMintrinsic,
    LLVMno_typeinfo,
    LLVMno_moduleinfo,
    LLVMalloca,
    LLVMva_start,
    LLVMva_copy,
    LLVMva_end,
    LLVMva_arg,
    LLVMldc,
    LLVMinline_asm
};