Fix various issues with invalid file operations:

• Add invfo_rdwr() (for read and write), invfo_ioctl(), invfo_poll(), and invfo_kqfilter() for use by file types that do not support the respective operations. Home-grown versions of invfo_poll() were universally broken (they returned an errno value, invfo_poll() uses poll_no_poll() to return an appropriate event mask). Home-grown ioctl routines also tended to return an incorrect errno (invfo_ioctl returns ENOTTY).
• Use the invfo_*() functions instead of local versions for unsupported file operations.
• Reorder fileops members to match the order in the structure definition to make it easier to spot missing members.
• Add several missing methods to linuxfileops used by the OFED shim layer: fo_write(), fo_truncate(), fo_kqfilter(), and fo_stat(). Most of these used invfo_*(), but a dummy fo_stat() implementation was added.