STM32 FLASH fixes: use size_t instead of uint16_t, make interface more generic.  From Freddie Chopin

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