Add doc for uncaughtException

doc/api.txt

@@ -85,6 +85,13 @@ more information.
                           +
                           The parameter +code+ is the integer exit code
                           passed to +process.exit()+.
+| +"uncaughtException"+        | +exception+ | Emitted when an exception 
+                                               bubbles all the way down to 
+                                               the event loop. If a listener
+                                               is added for this exception,
+                                               the default action (which is
+                                               to print a stack trace and
+                                               exit) will not occur. 
 | +"SIGINT"+, +"SIGUSR1"+, ... | (none)      | Emitted when the processes receives a signal.
                                                See sigaction(2) for a list of standard POSIX
                                                signal names such as SIGINT, SIGUSR1, etc.