Implement compatibility support for WRITE_SDCARD permission.

Now old applications will automatically be granted it.  Also renamed it from
SDCARD_WRITE to WRITE_SDCARD to be consistent with our other permissions,
and re-arranged how we do targetSdkVersion to actually be usuable for this
kind of stuff.

Note that right now this results in basically all apps being given the
WRITE_SDCARD permission, because their targetSdkVersion is not set.  I will
be dealing with that in a future change.
diff --git a/core/java/android/os/Build.java b/core/java/android/os/Build.java
index 5487c54..4a4285e 100644
--- a/core/java/android/os/Build.java
+++ b/core/java/android/os/Build.java
@@ -87,6 +87,12 @@
      */
     public static class VERSION_CODES {
         /**
+         * Magic version number for a current development build, which has
+         * not yet turned into an official release.
+         */
+        public static final int CUR_DEVELOPMENT = 10000;
+        
+        /**
          * October 2008: The original, first, version of Android.  Yay!
          */
         public static final int BASE = 1;
@@ -98,6 +104,19 @@
          * May 2009: Android 1.5.
          */
         public static final int CUPCAKE = 3;
+        /**
+         * Current work on "Donut" development branch.
+         * 
+         * <p>Applications targeting this or a later release will get these
+         * new changes in behavior:</p>
+         * <ul>
+         * <li> They must explicitly request the
+         * {@link android.Manifest.permission#WRITE_SDCARD} permission to be
+         * able to modify the contents of the SD card.  (Apps targeting
+         * earlier versions will always request the permission.)
+         * </ul>
+         */
+        public static final int DONUT = CUR_DEVELOPMENT;
     }
     
     /** The type of build, like "user" or "eng". */