NaCl: Fix irt_ppapi.h to compile with -Wstrict-prototypes

BUG=https://code.google.com/p/nativeclient/issues/detail?id=3114
TEST=compile

Review URL: https://codereview.chromium.org/312323005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@275297 0039d316-1c4b-4281-b951-d872f2087c98

ppapi/nacl_irt/public/irt_ppapi.h

@@ -14,7 +14,7 @@
 struct PP_StartFunctions {
   int32_t (*PPP_InitializeModule)(PP_Module module_id,
                                   PPB_GetInterface get_browser_interface);
-  void (*PPP_ShutdownModule)();
+  void (*PPP_ShutdownModule)(void);
   const void* (*PPP_GetInterface)(const char* interface_name);
 };