This commit changes the interrupt handler arrangement to support the PRI
interrupt on SH3 (a gap is needed between 0xaa0 and its helper).
It also introduces the use of the _gint_inth_callback function for the
callback, which provides dynamic TLB during the interrupt, and revealed
a bug about IMASK not being set automatically on SH3.
Finally, it sets the interrupt settings of the RTC more conservatively,
by wiping RCR1 and the carry, alarm and periodic interrupt flags during
initialization and context restoration.
Lephe
0622928f22
