include wcslib 6.2 in release 3.2

wcslib 6.1 was released:

WCSLIB version 6.1 (2018/10/19)
-------------------------------

* C library

  - Added support for time-related WCS keywords (Paper VII) by expanding
    the wcsprm struct to store them as auxiliary values, now filled by
    the header parsers, wcspih() and wcsbth() and handled routinely by
    wcsinit(), wcssub(), wcscompare(), wcsfree(), wcsprt(), wcsset(),
    and wcshdo().
   
  - Augmented datfix() to do various consistency checks on the new
    time-related keyvalues, and added a new routine, obsfix(), to check
    consistency of the OBSGEO-[XYZLBH] observatory coordinates.

  - In the usage notes for wcsbth(), clarified that, according to WCS
    Papers III and VII, certain global image header keywords are
    permitted in binary table headers and are expected to be inherited
    by image arrays and pixel lists, and elaborated on the difficulties
    that such inheritance may cause for pixel lists.

  - Extracted the definition of the wtbarr struct from wcs.h to a
    separate header file, wtbarr.h, in order to reduce the number of
    irrelevant warnings generated by 'gcc -Wpadded' (primarily for
    code development).  Applications code that needs to access members
    of the struct (unlikely) must now include wtbarr.h (or wcslib.h).
   
  - The WCSLIB major version number was incremented as changes to the
    wcsprm struct makes the ABI of the sharable library incompatible
    with executables linked with that of older releases.

* Installation

  - Several changes to configure and the makefiles aimed at facilitating
    code development.

* Fortran wrappers

  - Match changes to the C library, including adding a wrapper for
    obsfix().

[nden]

@astrofrog I worked on this over the weekend. I still have to figure out four test failures related to error messaging and write tests but am hopeful that I will post a PR before the feature freeze.

[astrofrog]

@nden - will you have any time to try and work on upgrading WCSLIB to 6.1 in time for the feature freeze? I’m working on adding time series functionality to the core package for the 3.2 release, and it would be really helpful to have the new WCS support for time axes.