Resolve the macro_unscope.hpp conflict by keeping both sets of #undefs
and regenerate the amalgamation.
The \u fast path from #5738 (get_codepoint_bulk) assumed that bulk
scanning implies lazy position tracking and advanced the adapter with a
bare bulk_skip(4). Stream adapters now scan in bulk but track position
and token eagerly, so a lone-surrogate error was reported 4 columns too
early. Advance through bulk_consume() instead.
Signed-off-by: Niels Lohmann <mail@nlohmann.me>