Allow starting Emacs --debug-init on Android

* doc/emacs/android.texi (Android Troubleshooting): Document
`debug-init' option.
* java/AndroidManifest.xml.in
(EmacsLauncherPreferencesActivity): New activity.  Export on
systems older than Android 7.0.
* java/org/gnu/emacs/EmacsActivity.java (onCreate): Adjust for
string startup argument.
* java/org/gnu/emacs/EmacsLauncherPreferencesActivity.java: New
file.
* java/org/gnu/emacs/EmacsPreferencesActivity.java
(EmacsPreferencesActivity): Don't make final.
(startEmacsQ): Give start-up argument as an argument, not as a
boolean.
(startEmacsDebugInit): New function.
(onCreate): Register new listener; make final.
* java/org/gnu/emacs/EmacsService.java (onCreate): Pass
extraStartupArgument.
* java/org/gnu/emacs/EmacsThread.java (EmacsThread): Rename
startDashQ to extraStartupArgument.
(run): Adjust accordingly.
* java/res/values-v24/bool.xml:
* java/res/values/bool.xml:
* java/res/values/strings.xml: New files.
* java/res/xml/preferences.xml: Add new option.  Move string
resources around.

1 files changed, 17 insertions, 0 deletions

diff --git a/java/AndroidManifest.xml.in b/java/AndroidManifest.xml.in
index f7f834e7582..082c4c9373e 100644
--- a/java/AndroidManifest.xml.in
+++ b/java/AndroidManifest.xml.in
@@ -180,6 +180,23 @@ along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>. -->
       </intent-filter>
     </activity>
 
+    <!-- Android 6 and earlier don't display ``application
+         preferences'' activities in Settings, so display the
+         preferences activity as a launcher icon instead.  -->
+
+    <activity android:autoRemoveFromRecents="true"
+              android:label="Emacs options"
+              android:enabled="@bool/isBeforeNougat"
+              android:exported="@bool/isBeforeNougat"
+              android:icon="@drawable/emacs_wrench"
+              android:name=".EmacsLauncherPreferencesActivity">
+      <intent-filter>
+        <action android:name="android.intent.action.MAIN" />
+        <category android:name="android.intent.category.DEFAULT" />
+        <category android:name="android.intent.category.LAUNCHER" />
+      </intent-filter>
+    </activity>
+
     <provider android:name="org.gnu.emacs.EmacsDocumentsProvider"
               android:authorities="org.gnu.emacs"
               android:exported="true"