Use aver not assert.

* src/output.c: Don't include assert.h.
(output_skeleton): Use aver not assert.
* src/system.h (aver): In documentation of why, add links to
Paul Eggert's explanations in the mailing lists.
(cherry picked from commit 9789acf091)

ChangeLog

@@ -1,3 +1,11 @@
+2009-09-03  Joel E. Denny  <[email protected]>
+
+	Use aver not assert.
+	* src/output.c: Don't include assert.h.
+	(output_skeleton): Use aver not assert.
+	* src/system.h (aver): In documentation of why, add links to
+	Paul Eggert's explanations in the mailing lists.
+
 2009-09-05  Alex Rozenman  <[email protected]>
 
 	Use "Unresolved reference" error message when no symbols were found