[boost] [conversion] Serious header integrity test failures.

This integrity test verifies that every header file present in svn branches/release and trunk is also present in git master and develop, respectively, and visa versa. The branches/release vs master comparison is in pretty good shape - no missing headers, but a small number of extra headers. Two libraries are affected. But the trunk vs develop comparison turned up problems in many libraries. For example, the whole Boost.Chrono stopwatches sub-directory is missing. These look serious. What is the fix? --Beman