feat: add user_data API test and reorder WrenErrorFn vm parameter to first position

Add a new test suite for user data get/set operations on WrenVM, including
a Wren script that validates default NULL userData, retrieval after VM
creation, and mutation via wrenSetUserData. Also reorder the vm parameter
in WrenErrorFn callback signature and all its call sites to match the
convention used by other callback types, updating the typedef, the
reportError implementation, and all invocations in the compiler and
debug modules. Include the new source and header files in the Xcode
project build configuration.

test/api/main.c

@@ -15,6 +15,7 @@
 #include "reset_stack_after_call_abort.h"
 #include "reset_stack_after_foreign_construct.h"
 #include "slots.h"
+#include "user_data.h"
 
 // The name of the currently executing API test.
 const char* testName;
@@ -59,6 +60,9 @@ static WrenForeignMethodFn bindForeignMethod(
   
   method = slotsBindMethod(fullName);
   if (method != NULL) return method;
+  
+  method = userDataBindMethod(fullName);
+  if (method != NULL) return method;
 
   fprintf(stderr,
       "Unknown foreign method '%s' for test '%s'\n", fullName, testName);

test/api/user_data.c

@@ -0,0 +1,51 @@
+#include <string.h>
+
+#include "user_data.h"
+
+static const char* data = "my user data";
+static const char* otherData = "other user data";
+
+static void test(WrenVM* vm)
+{
+  WrenConfiguration configuration;
+  wrenInitConfiguration(&configuration);
+  
+  // Should default to NULL.
+  if (configuration.userData != NULL)
+  {
+    wrenSetSlotBool(vm, 0, false);
+    return;
+  }
+  
+  configuration.userData = (void*)data;
+  
+  WrenVM* otherVM = wrenNewVM(&configuration);
+  
+  // Should be able to get it.
+  if (wrenGetUserData(otherVM) != data)
+  {
+    wrenSetSlotBool(vm, 0, false);
+    wrenFreeVM(otherVM);
+    return;
+  }
+  
+  // Should be able to set it.
+  wrenSetUserData(otherVM, (void*)otherData);
+  
+  if (wrenGetUserData(otherVM) != otherData)
+  {
+    wrenSetSlotBool(vm, 0, false);
+    wrenFreeVM(otherVM);
+    return;
+  }
+
+  wrenSetSlotBool(vm, 0, true);
+  wrenFreeVM(otherVM);
+}
+
+WrenForeignMethodFn userDataBindMethod(const char* signature)
+{
+  if (strcmp(signature, "static UserData.test") == 0) return test;
+
+  return NULL;
+}

test/api/user_data.h

@@ -0,0 +1,3 @@
+#include "wren.h"
+
+WrenForeignMethodFn userDataBindMethod(const char* signature);

test/api/user_data.wren

@@ -0,0 +1,5 @@
+class UserData {
+  foreign static test
+}
+
+System.print(UserData.test) // expect: true