This is a circuit I use to save board space.
It uses the MAX233 IC as both RS-232 interface
and power-up system reset timer.
Here's a JPEG schematic.
This should work with the MAX232 as well (with appropriate
pinout adjustments...)
The 1N4148 diode dumps the capacitor on loss of Vcc. The 100 ohm
resistor limits the reset pushbutton (cap. discharge) current.

If you're worried that a diode short might result in smoke, put
the 100 ohm resistor in series with the pushbutton.