add SPM12 versions r7487 and r7771

[gllmflndn]

• add link to recent SPM12 updates:
  /~https://github.com/spm/spm12/releases
• use HTTPS on documentation links
• define a new environment variable to prevent a crash with some Linux distributions.,

[codecov]

Codecov Report

Merging #319 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #319   +/-   ##
=======================================
  Coverage   74.58%   74.58%           
=======================================
  Files          33       33           
  Lines        1853     1853           
  Branches      241      241           
=======================================
  Hits         1382     1382           
  Misses        371      371           
  Partials      100      100           

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[satra]

thanks @gllmflndn