[NFC][OCaml] Resolve a couple more compilation warnings

[jberdine]

Summary

Followup to: 0b1dc49ca38a [NFC][OCaml] Resolve const and unsigned compilation warnings

llvm/bindings/ocaml/llvm/llvm_ocaml.c

 \*===----------------------------------------------------------------------===*/
 
 #include <assert.h>
 #include <stdlib.h>
 #include <string.h>
 #include "llvm-c/Core.h"
 #include "llvm-c/Support.h"
 #include "llvm/Config/llvm-config.h"
 #include "caml/memory.h"
 #include "caml/fail.h"
 #include "caml/callback.h"
 
 #include "llvm_ocaml.h"
 
 value llvm_string_of_message(char* Message) {
   value String = caml_copy_string(Message);
   LLVMDisposeMessage(Message);

 
 /* llcontext -> llvalue */
 CAMLprim LLVMValueRef llvm_mdnull(LLVMContextRef C) {
   return NULL;
 }
 
 /* llvalue -> string option */
 CAMLprim value llvm_get_mdstring(LLVMValueRef V) {
-  size_t Len;
+  unsigned Len;
   const char *CStr = LLVMGetMDString(V, &Len);
   return cstr_to_string_option(CStr, Len);
 }
 
 CAMLprim value llvm_get_mdnode_operands(LLVMValueRef V) {
   CAMLparam0();
   CAMLlocal1(Operands);
   unsigned int n;

llvm/bindings/ocaml/target/target_ocaml.c

 |* Note that these functions intentionally take liberties with the CAMLparamX *|
 |* macros, since most of the parameters are not GC heap objects.              *|
 |*                                                                            *|
 \*===----------------------------------------------------------------------===*/
 
 #include "llvm-c/Core.h"
 #include "llvm-c/Target.h"
 #include "llvm-c/TargetMachine.h"
 #include "caml/alloc.h"
 #include "caml/fail.h"
 #include "caml/memory.h"
 #include "caml/custom.h"
 #include "caml/callback.h"
 
 void llvm_raise(value Prototype, char *Message);
 value llvm_string_of_message(char* Message);
 
CAMLprim value llvm_targetmachine_set_verbose_asm(value Verb, value Machine) {
   return Val_unit;
 }
 
 /* Llvm.llmodule -> CodeGenFileType.t -> string -> TargetMachine.t -> unit */
 CAMLprim value llvm_targetmachine_emit_to_file(LLVMModuleRef Module,
                             value FileType, value FileName, value Machine) {
   char *ErrorMessage;
 
   if(LLVMTargetMachineEmitToFile(TargetMachine_val(Machine), Module,
-                                 String_val(FileName), Int_val(FileType),
-                                 &ErrorMessage)) {
+                                 (char *)String_val(FileName),
+                                 Int_val(FileType), &ErrorMessage)) {
     llvm_raise(*caml_named_value("Llvm_target.Error"), ErrorMessage);
   }
 
   return Val_unit;
 }
 
 /* Llvm.llmodule -> CodeGenFileType.t -> TargetMachine.t ->
    Llvm.llmemorybuffer */