* pull request to make date-time all inline (#135)
* remove legacy to_simple_string and prefer streaming in test code
* driveby fix to clean up self-assign compiler warnings in test code
* driveby fix to clean up unused variable compiler warnings in test code
* another update for issue #123 (constexpr) to allow time_duration constexpr to work
* final updates to make date_time free of library - issue #134
* add stub library for backward compatibility (#137)
* remove legacy to_simple_string and prefer streaming in test code
* driveby fix to clean up self-assign compiler warnings in test code
* driveby fix to clean up unused variable compiler warnings in test code
* another update for issue #123 (constexpr) to allow time_duration constexpr to work
* final updates to make date_time free of library - issue #134
* make a stub library for backward compatibility of libs that link date_time library
* suppressed const qualifier on function return type (#138)
* suppressed const qualifier on function return type
As warned in https://www.boost.org/development/tests/develop/output/teeks99-dkr-dg4-6-warn-date_time-gcc-4-6~c++0x~warn-warnings.html#hours_special_value
```../boost/date_time/gregorian/greg_weekday.hpp:52:41: warning: type qualifiers ignored on function return type [-Wignored-qualifiers]
../boost/date_time/gregorian/greg_weekday.hpp:61:40: warning: type qualifiers ignored on function return type [-Wignored-qualifiers]```
* trivial commit to trigger CI
* fix c++2a ambiguity on clang10 with operator== issue #132 (#140)
Co-authored-by: joaquintides <joaquin.lopezmunoz@gmail.com>
