Fix COI compilation

[carlopi]

Problem: extern C and includes are not friends

Arrow submodule vendors in xxhash, and the vendored in apache-arrow does a funny:

extern 'C' {

#include <something>

} 

Problem? This propagates C-linkage to the header, that then will eventually #include <emscripten.h>, that since it relies on template code can't be compiled with C-linkage.

xxhash should move includes outside of extern C brackets, I will raise a bug report there.

I am not sure/I don't see if situation can be detected / handled at the emscripten.h level. Basic open question is: can a header know it's being compiled within a extern 'C' namespace?

Solution: ... patches!

As always, adding more layers of patching solves (most) problems connected to customising submodules, at least in the short term. Here the patch explicitly includes emscripten.h outside of the extern C code.

I moved other patches from duckdb_patches to the more structured patches/duckdb, so that now also a patches/arrow can be added.

[carlopi]

Issue raising this on the Cyan4973/xxHash repository: Cyan4973/xxHash#960.

For the patch to be removed that has to go in, a new version being released, and arrow bumping vendored dependency to newer version, and us bumping arrow dependency.