Merge some old datetime changes to release

- [70756] Convert jamfile for examples to boost build v2.
- [79211][79212] Suppress g++4.6 warnings in tests.
- Document NO LIB option. Fixes #6077.


[SVN r80629]

libs/date_time

@@ -1 +1 @@
-Subproject commit 006adfaa84aa19a34da3ede6563882df00335c81
+Subproject commit 693c89198f7b378f419037a72b13bf1195810a7d