Exit after the user's session has finished.  This works around slim's broken
PAM session handling (see
http://developer.berlios.de/bugs/?func=detailbug&bug_id=19102&group_id=2663).

Patch by Eelco Dolstra, from Nixpkgs.

--- slim-1.3.6/app.cpp	2013-10-15 11:02:55.629263422 +0200
+++ slim-1.3.6/app.cpp	2013-10-15 13:00:10.141210784 +0200
@@ -816,7 +822,7 @@
 	StopServer();
 	RemoveLock();
 	while (waitpid(-1, NULL, WNOHANG) > 0); /* Collects all dead childrens */
-	Run();
+	exit(OK_EXIT);
 }
 
 void App::KillAllClients(Bool top) {
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<tr><td><span title='2018-03-20 14:22:06 -0400'>2018-03-20</span></td><td><a href='/guix/commit/gnu/packages/tbb.scm?id=ac21be848ac420d2106d4441e9e48ea6a60c5c8c'>Merge branch 'master' into core-updates</a></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2018-03-20 17:17:58 +0100'>2018-03-20</span></td><td><a href='/guix/commit/gnu/packages/tbb.scm?id=4a78fd4617908546be15d2c101f5cab512c71f8e'>Correct name and Email for ng0.</a><span class='msg-avail'>...</span></td><td>ng0</td></tr>
<tr><td><span title='2018-03-16 09:08:31 -0400'>2018-03-16</span></td><td><a href='/guix/commit/gnu/packages/tbb.scm?id=6cbee49d6668eb7fd738080666f66febfce8c7e8'>gnu: All snippets report errors using exceptions, else return #t.</a><span class='msg-avail'>...</span></td><td>Mark H Weaver</td></tr>
<tr><td><span title='2016-10-08 00:03:24 +0200'>2016-10-08</span></td><td><a href='/guix/commit/gnu/packages/tbb.scm?id=e35ce6893c7b45730979fb61a669488de321dec8'>gnu: tbb: Update to 2017_20160916.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2016-09-26 14:30:58 +0200'>2016-09-26</span></td><td><a href='/guix/commit/gnu/packages/tbb.scm?id=1a545a1e7c30db76e562af527673081b490c4a11'>gnu: tbb: Fail on test errors.</a><span class='msg-avail'>...</span></td><td>Ricardo Wurmus</td></tr>
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