Implement -list-cores UI option

Also fixed a bug in iolooper-select.c (io_looper_del_write was buggy)
Also switched iolooper-select.c to use malloc/free instead of qemu_xxx

Change-Id: Ief47608f30a863d624af6363620e93e903cbdadc
diff --git a/android/help.c b/android/help.c
index f589b3e..2103b00 100644
--- a/android/help.c
+++ b/android/help.c
@@ -1010,6 +1010,18 @@
 }
 #endif  // CONFIG_MEMCHECK
 
+#ifdef CONFIG_STANDALONE_UI
+static void
+help_list_cores(stralloc_t*  out)
+{
+    PRINTF(
+    "  use '-list-cores localhost to list emulator core processes running on this machine.\n"
+    "  use '-list-cores host_name, or IP address to list emulator core processes running on\n"
+    "  a remote machine.\n"
+    );
+}
+#endif  // CONFIG_STANDALONE_UI
+
 static void
 help_show_kernel(stralloc_t*  out)
 {