Starlink-pyast

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- A new method call astMapDefined has been added to the KeyMap class.
It checks if a gtiven key name has a defined value in a given KeyMap.

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- A bug has been fixed in FitsChan that caused inappropriate CTYPE values
to be generated when writing a FrameSet to FITS-WCS headers if the
current Frame describes generalised spherical coordinates (i.e. a
SkyFrame with System=Unknown).

- When a FitsChan is used to write an "offset" SkyFrame (see attribute
SkyRefIs) to a FITS-WCS encoded header, two alternate axis descriptions
are now created - one for the offset coordinates and one for the absolute
coordinates. If such a header is subsequently read back into AST, the
original offset SkyFrame is recreated.

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- IMPORTANT! The default behaviour of astRebinSeq is now NOT to conserve
flux. To conserve flux, the AST__CONSERVEFLUX flag should be supplied
when calling astRebinSeq. Without this flag, each output value is a
weighted mean of the neighbouring input values.

- A new flag AST__NONORM can be used with astRebinSeq<X> to indicate that
normalisation of the output arrays is not required. In this case no
weights array need be supplied.

- A bug has been fixed in astAddFrame (AST_ADDFRAME) method that could
result in the incorrect inversion of Mappings within the FrameSet when
the AST__ALLFRAMES flag is supplied for the "iframe" parameter.

- The astRate method has been re-written to make it faster and more
reliable.

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- A bug has been fixed in astRebinSeq<X> which could result in
incorrect normalisation of the final binned data and variance values.

- When reading a FrameSet from a FITS-DSS header, the keywords CNPIX1 and
CNPIX2 now default to zero if absent. Previously an error was reported.

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- The FitsChan class can now read FITS headers that use the SAO
convention for representing distorted TAN projections, based on the use
of "COi_j" keywords to hold the coefficients of the distortion polynomial.

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- The previously private grf3d.h header file is now installed into
prefix/include.