Update doc/efun/ aus Driversourcen.

Manpages der efuns aktualisiert, neue Manpages hinzugefuegt.

Change-Id: I7cc91684269ff56d1aef47d5c5e7c87f7fd531dc
diff --git a/doc/efun/this_coroutine b/doc/efun/this_coroutine
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+SYNOPSIS
+        coroutine this_coroutine()
+
+DESCRIPTION
+        Returns the innermost coroutine in the caller stack.
+        Returns 0 if there is no coroutine.
+
+HISTORY
+        Coroutines were introduced in LDMud 3.6.5.
+
+SEE ALSO
+        coroutines(LPC), call_coroutine(E)