Reported by Rob Vermaas' Hydra build farm on x86_64-darwin 10.2.0 with
G++ 4.6.3.
* tests/headers.at (Several parsers): Include AT_DATA_SOURCE_PROLOGUE
in the files to compile.
* data/location.cc: Do not include twice string and iostream (once
by position.hh, and then by location.hh).
* README-hacking (Typical errors): Some hints for other maintainers.