ML2KApp

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   Approximate eccentric longitude from the mean longitude.
   Uses a series approximation to Kepler's equation. 
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   Form:
   eccLong = ML2KApp( P1, P2, meanLong )
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   Inputs
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   P1                   e sin(longitude of pericenter)
   P2                   e cos(longitude of pericenter)
   meanLong             Mean longitude

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   Outputs
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   eccLong              Eccentric longitude (K)

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   References:   Battin, R.H., An Introduction to the Methods and Mathematics
                 of Astrodynamics, AIAA, New York, 1987, p. 196.
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