This commit was manufactured by cvs2svn to create branch 'RC_1_31_0'.

[SVN r21427]
update version number


[SVN r21484]
merged changes from main branch


[SVN r21574]
merge shadow changes from main branch


[SVN r21606]
fix unused var warning


[SVN r21617]
update for bi-directional changes


[SVN r21825]
fix doc for span


[SVN r21827]
various updates for 1.31 release


[SVN r21834]
a couple minor documentation updates


[SVN r22109]
cleanup of licensing links


[SVN r22116]
additional acknowledgements


[SVN r22123]
update compiler status summary and limitation info


[SVN r22125]