Repair windows build break.

Forgot to isolate extern declaration, mac/linux had no problem,
but windows breaks.

Change-Id: Ib09119661225193d9cfb1cd9118b78cf7d9bd2f4

include/LibreOfficeKit/LibreOfficeKitInit.h

@@ -244,8 +244,10 @@ typedef LibreOfficeKit *(LokHookFunction2)( const char *install_path, const char
 
 typedef int             (LokHookPreInit)  ( const char *install_path, const char *user_profile_url );
 
+#if defined(IOS)
 extern __attribute__ ((visibility("default")))
     LibreOfficeKit *libreofficekit_hook_2(const char* install_path, const char* user_profile_path);
+#endif
 
 static LibreOfficeKit *lok_init_2( const char *install_path,  const char *user_profile_url )
 {