The library is header only. It makes no sense to distinuish
between the standard the library is compiled with and the
standard the tests are compiled with. The library does not
get compiled on its own.
* value: add missing includes
* mysql, sqlite3: use explicitly *out* stringstreams for serialization
* postgresql: fix: use max_digits10 instead of digits10
* detail: add float_safe_ostringstream, ensuring floats are serialized with enough precision
* mysql, postgresql, sqlite3, tests: fix: set float-precision for all streams
* run clang-format on changed files
* inline remove_cvref.h
* replace unspecific "wrapper" with concrete type name
* tests: split connector specific tests out of serialize/Float
