#includes should use C++ form rather than C form

[Richard Boulton]

According to xapian-core/HACKING:

For standard ISO C headers, we now prefer the C++ form for ISO C headers (e.g. "#include <cstdlib>" rather than "#include <stdlib.h>") for new code (a *lot* of the existing code currently uses the old form, but there are a few semantic differences, so we're holding off on a wholesale conversion until 1.1.0 to avoid potentially disruptive changes with no direct benefit to users).

This ticket is just to remind us to do this. Since 1.1.x is a development series, I don't think it needs to be done for 1.1.0, but I'm marking this for 1.1.0 since we should at least change HACKING if we don't do it for that release.

[Olly Betts]

I think making this change would be unhelpful while we have several unmerged branches and unapplied patches as it will touch a lot of files and create conflicts in many cases. It'll also add work when backporting some fixes too. But it would be good to do it a decent time before 1.2.0 in case it causes any problems.

I don't see this needs to block 1.1.0 either - "until 1.1.0" could mean "until after 1.1.0" - but feel free to reword if you want.

[Olly Betts]

r12351 makes this change to xapian-core's examples subdirectory and r12352 to bin. Those two should cause conflicts with unmerged branches I hope. Triaging the rest to 1.1.4.

[Olly Betts]

Fixed for xapian-core in r13002. Fixed for omega in r13003 except uses of stdint.h - I worry about portability of cstdint since stdint.h was added by C99. Uses in xapian-bindings are generated by SWIG. Script to update automatically in xapian-maintainer-tools/c++stdcheaders so that branches can be easily updated and to fix any future regressions.