Remove unix/io_page.ml

[yallop]

There are currently two almost-identical modules in the repository:

• unix/io_page.ml
• lib/io_page.ml

The first of these has fallen into disrepair; for example, it includes the external declaration:

external alloc_pages: int -> t = "caml_alloc_pages"

which no longer matches the signature of caml_alloc_pages, which now has two arguments.

A related problem is that the C code for caml_alloc_pages is built as part of the "unix" library (io-page.unix), but used in the "lib" library (io-page).

This PR removes the obsolete unix/io_page.ml module and moves the C code for caml_alloc_pages into the io-page library.

[talex5]

I think the C code needs to stay in .unix because on Xen we have a different implementation (or at least, we compile it with different flags). Would be good to move that code here from mirage-platform too.

[yomimono]

This seems like a step in the right direction. Coincidentally I was just looking at #19 , which goes even farther in proposing removal of io-page code.

[yallop]

Ok, I'll trim this PR down a bit to just remove the dead code.

[hannesm]

@talex5 uhm, in general stub code from specific libraries should move away from mirage-platform, since it is a pain to remember updating the library x (e.g. cstruct), and than adjust the stubs in mirage-platform... (see also mirage/mirage-platform#124)

[talex5]

@hannesm yes, I think that's what I said. Move the code from mirage-platform to io-page.

[hannesm]

oh, sorry, misread.

[djs55]

If I understand correctly then

• everyone agrees that stubs should move into the library they belong to. However we haven't figured out how to build the Xen code properly (or at least I haven't)
• the unix/io_page.ml{,i} appear to be unused and should be deleted as in this PR
• the io_page.unix sub package is still needed and contains the Unix stubs so shouldn't be removed from the _oasis -- I'll see if I can adjust this patch.