This patch consolidates all the non cancellable fcntl calls to use
the __fcntl_nocancel identifier. For non cancellable targets it will
be just a macro to call the default respective symbol while on Linux
will be a internal one.
Since its prototype is already defined at internal fcntl.h header, it
is removed from not-cancel.h one.
Checked on x86_64-linux-gnu, x86_64-linux-gnu-x32, and i686-linux-gnu.