Move apache specific portions of android.net.http to external/apache-http.

We continue to compile external/apache-http into ext.jar. This contains
a few changes apart fom the classes moving around :

- Makefile changes to build docs and api-stubs for now. A future change
  will revert these changes and remove these classes from stubs and
  docs.
- Hardcode event IDs in legacyerrorstrings to avoid a dependency between
  the frameworks and apache. These strings are on their way out and will
  never change anyway.
- Remove imports due to {@link} tags and use {@code} instead.
- Remove an accidental(?) dependency on apache commons code that's a
  part of apache-http.

bug: 18027885

Change-Id: I51cd038d846ec7d02c283a4541b10a6a9cf62ecf

core/java/android/net/ProxyInfo.java

@@ -21,8 +21,6 @@ import android.os.Parcel;
 import android.os.Parcelable;
 import android.text.TextUtils;
 
-import org.apache.http.client.HttpClient;
-
 import java.net.InetSocketAddress;
 import java.net.URLConnection;
 import java.util.List;
@@ -31,8 +29,9 @@ import java.util.Locale;
 /**
  * Describes a proxy configuration.
  *
- * Proxy configurations are already integrated within the Apache HTTP stack.
- * So {@link URLConnection} and {@link HttpClient} will use them automatically.
+ * Proxy configurations are already integrated within the {@code java.net} and
+ * Apache HTTP stack. So {@link URLConnection} and Apache's {@code HttpClient} will use
+ * them automatically.
  *
  * Other HTTP stacks will need to obtain the proxy info from
  * {@link Proxy#PROXY_CHANGE_ACTION} broadcast as the extra {@link Proxy#EXTRA_PROXY_INFO}.