wartershed SEG_INDEX macro

This macro is fine and is used fine in the code. I suspect an AIX
compiler problem. I have run across compilers that can't handle the
full implications of K&R C. I suspect the macro is one of those
cases where the compiler is generating incorrect code. Take this
up with IBM. They would want to know about it.

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Michael Shapiro U.S. Army CERL
email: shapiro@zorro.cecer.army.mil Environmental Division
phone: (217) 352-6511 ext 526 P.O. Box 9005
fax: (217) 373-7222 Champaign, Ill. 61826-9005
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