Make new event trigger facility actually do something.

Commit 3855968f32 added syntax, pg_dump,
psql support, and documentation, but the triggers didn't actually fire.
With this commit, they now do.  This is still a pretty basic facility
overall because event triggers do not get a whole lot of information
about what the user is trying to do unless you write them in C; and
there's still no option to fire them anywhere except at the very
beginning of the execution sequence, but it's better than nothing,
and a good building block for future work.

Along the way, add a regression test for ALTER LARGE OBJECT, since
testing of event triggers reveals that we haven't got one.

Dimitri Fontaine and Robert Haas

src/port/qsort.c

@@ -193,3 +193,12 @@ loop:SWAPINIT(a, es);
 	}
 /*		qsort(pn - r, r / es, es, cmp);*/
 }
+
+/*
+ * qsort wrapper for strcmp.
+ */
+int
+pg_qsort_strcmp(const void *a, const void *b)
+{
+	return strcmp(*(char *const *) a, *(char *const *) b);
+}