detail::is_sax had no user: the parser and the binary reader only use
is_sax_static_asserts, so is_sax was a second, unchecked copy of the
SAX event list. is_sax_static_asserts asserted boolean(bool) twice in
a row, and detail::is_detected_convertible was never used anywhere.
Remove all three and include <cstddef> for size_t instead of <cstdint>.
Only names in nlohmann::detail are removed; behavior, public API and ABI
are unchanged. The diagnostics for an incomplete SAX handler are the
same, apart from the duplicated boolean() message.
Part of #5708
Signed-off-by: Niels Lohmann <mail@nlohmann.me>
Niels Lohmann
4c208728e7