Follow the approach of newlib to use a file sys/_types.h to specify the
underlying type for POSIX/libc types that must be provided in multiple
headers. The identifier for this type is in the reserved namespace.
Use this type rather than a specific standard type in all headers that
need to provide the type under its public name.
Remove the inclusion of <sys/types.h> from headers that should not bring
in all symbols present in that header, replacing it with the standard
boilerplate to expose the specific symbols that are required.
Signed-off-by: Peter A. Bigot <pab@pabigot.com>
ef4cd6a1ab