remove some STATUS_* symbols

I have found the collection of STATUS_* defines in c.h a bit curious. 
There used to be a lot more even that have been removed over time. 
Currently, STATUS_FOUND and STATUS_WAITING are only used in one group of 
functions each, so perhaps it would make more sense to remove these from 
the global namespace and make them a local concern.

Attached are two patches to remove these two symbols.  STATUS_FOUND can 
be replaced by a simple bool.  STATUS_WAITING is replaced by a separate 
enum.

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Peter Eisentraut              http://www.2ndQuadrant.com/
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