mingw: Add body for virFork and remove double virDriverLoadModule export

Commit 9bd3cce0 added virFork and
virDriverLoadModule to libvirt_private.syms, but virFork didn't have
a body on Win32 and virDriverLoadModule was already correctly
exported conditional via libvirt_driver_modules.syms.

src/libvirt_private.syms

@@ -314,10 +314,6 @@ virDomainConfNWFilterTeardown;
 virDomainConfVMNWFilterTeardown;
 
 
-# driver.h
-virDriverLoadModule;
-
-
 # ebtables.h
 ebtablesAddForwardAllowIn;
 ebtablesAddForwardPolicyReject;

src/util/util.c

@@ -927,6 +927,15 @@ virExecDaemonize(const char *const*argv ATTRIBUTE_UNUSED,
     return -1;
 }
 
+int
+virFork(pid_t *pid)
+{
+    *pid = -1;
+    errno = ENOTSUP;
+
+    return -1;
+}
+
 # endif /* WIN32 */
 
 int