Upgrade Android build to Gradle build system

The old Ant build system has been deprecated for a while and new development is focused on Gradle.
I also removed a hardcoded string that lint caught and moved the patch files to a subdirectory.
I left the JNI files in the root directory.

build/android/src/main/java/net.minetest.minetest/MinetestTextEntry.java

@@ -0,0 +1,91 @@
+package net.minetest.minetest;
+
+import android.app.Activity;
+import android.app.AlertDialog;
+import android.content.DialogInterface;
+import android.content.Intent;
+import android.os.Bundle;
+import android.text.InputType;
+import android.util.Log;
+import android.view.KeyEvent;
+import android.view.View;
+import android.view.View.OnKeyListener;
+import android.widget.EditText;
+
+public class MinetestTextEntry extends Activity {
+	public AlertDialog mTextInputDialog;
+	public EditText mTextInputWidget;
+	
+	private final int MultiLineTextInput              = 1;
+	private final int SingleLineTextInput             = 2;
+	private final int SingleLinePasswordInput         = 3;
+	
+	@Override
+	public void onCreate(Bundle savedInstanceState) {
+		super.onCreate(savedInstanceState);
+		
+		Bundle b = getIntent().getExtras();
+		String acceptButton = b.getString("EnterButton");
+		String hint         = b.getString("hint");
+		String current      = b.getString("current");
+		int    editType     = b.getInt("editType");
+		
+		AlertDialog.Builder builder = new AlertDialog.Builder(this);
+		mTextInputWidget = new EditText(this);
+		mTextInputWidget.setHint(hint);
+		mTextInputWidget.setText(current);
+		mTextInputWidget.setMinWidth(300);
+		if (editType == SingleLinePasswordInput) {
+			mTextInputWidget.setInputType(InputType.TYPE_CLASS_TEXT | 
+					InputType.TYPE_TEXT_VARIATION_PASSWORD);
+		}
+		else {
+			mTextInputWidget.setInputType(InputType.TYPE_CLASS_TEXT);
+		}
+		
+		
+		builder.setView(mTextInputWidget);
+		
+		if (editType == MultiLineTextInput) {
+			builder.setPositiveButton(acceptButton, new DialogInterface.OnClickListener() {
+				public void onClick(DialogInterface dialog, int whichButton) 
+				{ pushResult(mTextInputWidget.getText().toString()); }
+				});
+		}
+		
+		builder.setOnCancelListener(new DialogInterface.OnCancelListener() {
+			public void onCancel(DialogInterface dialog) {
+				cancelDialog();
+			}
+		});
+		
+		mTextInputWidget.setOnKeyListener(new OnKeyListener() {
+			@Override
+			public boolean onKey(View view, int KeyCode, KeyEvent event) {
+				if ( KeyCode == KeyEvent.KEYCODE_ENTER){
+
+					pushResult(mTextInputWidget.getText().toString());
+					return true;
+				}
+				return false;
+			}
+		});
+		
+		mTextInputDialog = builder.create();
+		mTextInputDialog.show();
+	}
+	
+	public void pushResult(String text) {
+		Intent resultData = new Intent();
+		resultData.putExtra("text", text);
+		setResult(Activity.RESULT_OK,resultData);
+		mTextInputDialog.dismiss();
+		finish();
+	}
+	
+	public void cancelDialog() {
+		setResult(Activity.RESULT_CANCELED);
+		mTextInputDialog.dismiss();
+		finish();
+	}
+}