Starlink-pyast

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- AST is now distributed under the Lesser GPL licence.

- Least squares fitting of N-dimensional polynomials is now done using
files copied from the C/C++ Minpack package (see
http://devernay.free.fr/hacks/cminpack/index.html).

- Use of the IAU SOFA library has been replaced by ERFA library, which is
a re-badged copy of SOFA distributed under a less restrictive license. A
copy of ERFA is included within AST.

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- By default, the simplification of Polygons no longer checks that the
edges are not bent by the simplification. A new attribute, SimpVertices,
can be set to zero in order to re-instate this check.

- The Polygon class has a new mathod, astConvex, that returns a Polygon
representing the shortest polygon (i.e. convex hull) enclosing a
specified set of pixel values within a supplied array.

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- The FitsChan class has new attributes CardName and CardComm, which hold
the keyword name and comment of the current card.

- When reading FITS-WCS headers that include polynomial distortion in the
SIP format, any inverse transformation specified in the header is now
ignored and a new inverse is created to replace it based on the supplied
forward transformation. Previously, an inverse was created only if the
header did not include an inverse. The accuracy of the inverse
transformation has also been improved, although it may now be slower to
evaluate in some circumstances.

- A bug has been fixed that could over-write the FitsChan CarLin attribute
with a non-zero value if the header contains a spectral axis.

- The default options for each newly created FitsChan can now be
specified via the environment variable FITSCHAN_OPTIONS.

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- Fix support for reading GLS projections from FITS headers.

- The KeyMap class has new sorting options "KeyAgeUp" and "KeyAgeDown" that
retain the position of an existing entry if its value is changed. See the
SortBy attribute.

- A bug has been fixed in FitsChan that caused CDELT keywords for sky
axes to be treated as radians rather than degrees when reading a FITS
header, if the corresponding CTYPE values included no projection code.

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- Fix bug that could cause a segmenatation fault when reading a FITS TNX
header.

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- IMPORTANT! The interface for the astRebinSeq<X> (AST_REBINSEQ) family
of functions has been changed in order to allow a greater number of
pixels to be pasted into the output array. In C, the "nused" parameter
is now a pointer to a "int64_t" variable, instead of a simple "int". In
Fortran, the NUSED argument for AST_REBINSEQ<X> is now an INTEGER*8.

APPLICATION CODE SHOULD BE CHANGED ACCORDINGLY TO AVOID SEGMENTATION
FAULTS AND OTHER ERRATIC BEHAVIOUR.

- Added a new facility to the FrameSet class to allow each Frame to be
associated with multiple Mappings, any one of which can be used to
connect the Frame to the other Frames in the FrameSet. The choice of
which Mapping to use is controlled by the new "Variant" attribute of the
FrameSet class.

- Mappings (but not Frames) that have a value set for their Ident attribute
are now left unchanged by the astSimplify (AST_SIMPLIFY) function.