ioctl() just dispatches to the corresponding vmethod of an fd.
fcntl() handles fdtable-level operations (so far doesn't handle
actually, returning "not implemented" error), and forwards
fd-specific operations to ioctl vmethod just the same (i.e.
ioctl and fcntl operations share the same namespace, but otherwise
disjoint).
Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>