Inclusion order for <limits.h> and <sys/mman.h>

[paddybyers]

deps/libeio/eio.c contains a conditional inclusion of <sys/mman.h>. The logic for this breaks on Android, because the relevant variable (_POSIX_MAPPED_FILES) is in <limits.h> which is currently included after the variable is tested.

Suggest fix is here:

1b6bd89
55b94d2

[paddybyers]

This is also an issue for master.

Suggested fix is here:

f3bd630