forked from Imagelibrary/rtems
* new-exceptions/bspsupport/ppc_exc_asm_macros.h, new-exceptions/bspsupport/ppc_exc.S, new-exceptions/bspsupport/README, new-exceptions/bspsupport/ppc_exc_hdl.c: Thomas Doerfler clarified (thanks!) that raising an exception and executing the 1st instruction is not an atomical operation. I added a fix to the code that checks if a lower-priority interrupt is under way: we now not only test if the 'lock' variable was set but also check if the interrupted PC points to the 'write lock' instruction. Added more comments and updated README.