The Intel PMC architectural events have encodings which are identical to
those of some non-architectural core events. This is not a problem in the
general case as long as there's an 1:1 mapping between the two, but there
are few exceptions. For example, 3CH_01H on Nehalem/Westmere represents
both unhalted-reference-cycles and CPU_CLK_UNHALTED.REF_P.
CPU_CLK_UNHALTED.REF_P on the aforementioned architectures does not measure
reference (i.e. bus) but TSC, so there's the need to disambiguate.
In order to avoid the namespace collision rename all the architectural
events in a way they cannot be ambigous and refactor the architectural
events handling function to reflect this change.
While here, per Jim Harris request, rename
iap_architectural_event_is_unsupported() to iap_event_is_architectural().

Discussed with:	jimharris
Reviewed by:	jimharris, gnn
Forgot to update UPDATING in head last night.
malloc(9) cannot return NULL if M_WAITOK flag is specified.
remove $Id$ (whitespace change)
Partial cleanup in preparation for upcoming changes:

- netmap_rx_irq()/netmap_tx_irq() can now be called by FreeBSD drivers
  hiding the logic for handling NIC interrupts in netmap mode.
  This also simplifies the case of NICs attached to VALE switches.
     Individual drivers will be updated with separate commits.

- use the same refcount() API for FreeBSD and linux

- plus some comments, typos and formatting fixes

Portions contributed by Michio Honda
use netmap_rx_irq() / netmap_tx_irq() to handle interrupts in
netmap mode, removing the logic from individual drivers.

(note: if_lem.c not updated yet due to some other pending modifications)