Fix: create missing partition images on demand.

The previous patch introduced a regression where, if the userdata
partition image was not present (e.g. userdata-qemu.img), it was
no longer created at startup, and the emulator would fail to run.

This patch fixes the issue.

As an added bonus, it also fixes -wipe-data to ensure that this
option also clears the cache partition, if any. For some reason
the latter was never properly cleared.

Change-Id: Ic97ffa0468da6a8889d64623efaf05148099311f
diff --git a/android/main.c b/android/main.c
index 363c923..9e2a7fb 100644
--- a/android/main.c
+++ b/android/main.c
@@ -78,6 +78,8 @@
 
 extern int qemu_milli_needed;
 
+extern bool android_op_wipe_data;
+
 /* the default device DPI if none is specified by the skin
  */
 #define  DEFAULT_DEVICE_DPI  165
@@ -706,6 +708,7 @@
         } else {
             hw->disk_dataPartition_initPath = NULL;
         }
+        android_op_wipe_data = opts->wipe_data;
 
         uint64_t     defaultBytes =
                 hw->disk_dataPartition_size == 0 ?