Z80: Move address environment switch from the task switchers to the interrupt handler.  That may save doing the action multiple times per interrupt

x86: Move address environment switch from the task switchers to the interrupt handler.  That may save doing the action multiple times per interrupt

SH: Move address environment switch from the task switchers to the interrupt handler.  That may save doing the action multiple times per interrupt

MIPS: Move address environment switch from the task switchers to the interrupt handler.  That may save doing the action multiple times per interrupt

AVR32: Move address environment switch from the task switchers to the interrupt handler.  That may save doing the action multiple times per interrupt

AVR32: Move address environment switch from the task switchers to the interrupt handler.  That may save doing the actin multiple times per interrupt

ARM: Move address environment switch from the task switchers to the interrupt handler.  That may save doing the actin multiple times per interrupt

ARM: Move address environment switch from the task switchers to the interrupt handler.  That may save doing the actin multiple times per interrupt

ADDRENV: Use a group flag to determine if there is an address environment (instead of the thread type)

Add group_addrenv() which will be called during context switches in order to change address environments.  Not yet hooked in

Add group_addrenv() which will be called during context switches in order to change address environments.  Not yet hooked in

Rename up_addrenv_assign() to up_addrenv_clone() and generalize its arguments so that can be used for other purposes

Fix confusion about what is a page of data and what is a page of L2 page table; restructure functions to reduce duplicated logic

Change when address environment is instantiated; there are/were locations where access is made to the allocation address environment when it is not yet in place