boost [math] excessive warnings via [lexical_cast] from [date_time] (and others) for clang 3.4?

From: Jeff Garland (azswdude_at_[hidden])
Date: 2020-03-24 13:58:56

In the regression tables the following warnings are coming out of math
config.  I'm trying to understand what this means given that 1) the tests
compile and execute fine, 2) the deadline is up,  and 3) several of the
cases are compiled in c++11 mode (is it pre conformance bc it's
clang3.4?).  I've seen this warning in other places that include
lexical_cast as well.  So sure I could go and define the macro to quiet
this, but seems like that should be done closest to the source.  In other
words maybe math should only tell us that in headers that have a real
issue?  Or will this soon be a real issue?

../boost/math/tools/config.hpp:42:9: warning: CAUTION: One or more
C++11 features were found to be unavailable [-W#pragma-messages]
../boost/math/tools/config.hpp:43:9: warning: CAUTION: Compiling
Boost.Math in pre-C++11 conformance modes is now deprecated and will
be removed from March 2021. [-W#pragma-messages]
../boost/math/tools/config.hpp:44:9: warning: CAUTION: Define
BOOST_MATH_DISABLE_DEPRECATED_03_WARNING to suppress this message.
[-W#pragma-messages]

Full examples
https://www.boost.org/development/tests/develop/developer/date_time.html
https://www.boost.org/development/tests/develop/output/teeks99-dkr-dc3-4-98-date_time-clang-linux-3-4~c++98-warnings.html#testc_local_adjustor