Merging branch 'spanTests'  into 'r21'.

See merge request !1829

Merging branch 'corr_cerr'  into 'r21'.

See merge request !1828

Merging branch 'assert_cerr'  into 'r21'.

See merge request !1818

Merging branch 'suppressWarnings'  into 'r21'.

See merge request !1660

Merging branch 'scale_API_3'  into 'r21'.

See merge request !1827

Merging branch 'scale_API_2'  into 'r21'.

See merge request !1826

Merging branch 'scale_API'  into 'r21'.

See merge request !1825

The `install_name_tool` warnings about the invalidation of the MacOS code signature are discarded:
```
install_name_tool: warning: changes being made to the file will invalidate the code signature in <filename>
```

There is no way to prevent that, as the library RPATHs must be changed to build
the MacOS package.

Resolves issue #578

Merging branch 'changelog'  into 'r21'.

See merge request !1824

Merging branch 'addPyExc'  into 'r21'.

See merge request !1821

Merging branch 'links2'  into 'r21'.

See merge request !1823

Merging branch 'physref'  into 'r21'.

See merge request !1822

Merging branch 'i674'  into 'r21'.

See merge request !1820

Merging branch 'i677'  into 'r21'.

See merge request !1819