various functions should return bool not a pointer

[eugene]

there are various functions which perform some operation and return the results
in a structure of some sort. of these functions, some are required to be passed
in an allocated structure since they use elements of the structure to define the
operation. Some of these functions return the pointer to the structure as well.

These should be changed to just return 'bool'. examples are below:

psVectorStats
psImageStats
psVectorFitPolynomial1D
psVectorClipFitPolynomial1D
(and equivalents)

[Paul Price]

The following functions (from the SDRS) unnecessarily returned a pointer that
was passed in:

psBitSetSet
psBitSetClear
psVectorHistogram
psVectorFitPolynomial1D
psVectorFitPolynomial2D
psVectorFitPolynomial3D
psVectorFitPolynomial4D
psVectorChiClipFitPolynomial4D
psImageStats
psImageHistogram
psImageFitPolynomial

They have been changed to return bool, both in the SDRS and the code.