[OCaml] Add GlobalIFunc value kind to OCaml API

[jberdine]

Summary

The GlobalIFunc value kind has not yet been added to the OCaml
API. This patch only extends the enum, so that e.g. classify_value
will not crash. No support for manipulating or building GlobalIFuncs
is added at this point.

[whitequark]

LGTM

bindings/ocaml/llvm/llvm.ml

module ValueKind = struct
   | ConstantExpr
   | ConstantFP
   | ConstantInt
   | ConstantPointerNull
   | ConstantStruct
   | ConstantVector
   | Function
   | GlobalAlias
+  | GlobalIFunc
   | GlobalVariable
   | UndefValue
   | Instruction of Opcode.t
 end
 
 module DiagnosticSeverity = struct
   type t =
   | Error

bindings/ocaml/llvm/llvm.mli

module ValueKind : sig
   | ConstantExpr
   | ConstantFP
   | ConstantInt
   | ConstantPointerNull
   | ConstantStruct
   | ConstantVector
   | Function
   | GlobalAlias
+  | GlobalIFunc
   | GlobalVariable
   | UndefValue
   | Instruction of Opcode.t
 end
 
 (** The kind of [Diagnostic], the result of [Diagnostic.severity d].
     See [llvm::DiagnosticSeverity]. *)
 module DiagnosticSeverity : sig

bindings/ocaml/llvm/llvm_ocaml.c

enum ValueKind {
   ConstantExpr,
   ConstantFP,
   ConstantInt,
   ConstantPointerNull,
   ConstantStruct,
   ConstantVector,
   Function,
   GlobalAlias,
+  GlobalIFunc,
   GlobalVariable,
   UndefValue,
   Instruction
 };
 
 /* llvalue -> ValueKind.t */
 #define DEFINE_CASE(Val, Kind) \
     do {if (LLVMIsA##Kind(Val)) CAMLreturn(Val_int(Kind));} while(0)
if (LLVMIsAInstruction(Val)) {
     CAMLlocal1(result);
     result = caml_alloc_small(1, 0);
     Store_field(result, 0, Val_int(LLVMGetInstructionOpcode(Val)));
     CAMLreturn(result);
   }
   if (LLVMIsAGlobalValue(Val)) {
     DEFINE_CASE(Val, Function);
     DEFINE_CASE(Val, GlobalAlias);
+    DEFINE_CASE(Val, GlobalIFunc);
     DEFINE_CASE(Val, GlobalVariable);
   }
   DEFINE_CASE(Val, Argument);
   DEFINE_CASE(Val, BasicBlock);
   DEFINE_CASE(Val, InlineAsm);
   DEFINE_CASE(Val, MDNode);
   DEFINE_CASE(Val, MDString);
   DEFINE_CASE(Val, UndefValue);

include/llvm-c/Core.h

macro(Constant)                         \
       macro(ConstantFP)                     \
       macro(ConstantInt)                    \
       macro(ConstantPointerNull)            \
       macro(ConstantStruct)                 \
       macro(ConstantTokenNone)              \
       macro(ConstantVector)                 \
       macro(GlobalValue)                    \
         macro(GlobalAlias)                  \
+        macro(GlobalIFunc)                  \
         macro(GlobalObject)                 \
           macro(Function)                   \
           macro(GlobalVariable)             \
       macro(UndefValue)                     \
     macro(Instruction)                      \
       macro(BinaryOperator)                 \
       macro(CallInst)                       \
         macro(IntrinsicInst)                \