P1243 Rangify New Algorithms

[jensmaurer]

P1243R1 Rangify New Algorithms (Dan Raviv)

https://issues.isocpp.org/show_bug.cgi?id=542

[mclow]

LEWG discussion in San Diego: http://wiki.edg.com/bin/view/Wg21sandiego2018/P1243
and https://issues.isocpp.org/show_bug.cgi?id=542

[mclow]

Reviewed on Thursday in LWG; update needed.

[mclow]

Found a bug in shift_left/right, needs updated paper. Will review between meetings.

[wg21bot]

P1243R2 Rangify New Algorithms (Dan Raviv)