cortex-r-rt v0.2.0

Added

• Added ABT und UND mode stack setup.
• Default exception handlers for undefined, prefetch abort and data abort exceptions
• SMP support
• Zeroing of registers on start-up
• #[entry] and #[exception] and #[interrupt] macros

Changed

• Fixed interrupt handler so interrupts can be re-entrant
• Default Rust exception handler is now an empty permanent loop instead of a semihosting exit.
• The SVC asm trampoline can now be over-ridden
• The Undefined, Prefetch and Abort handlers can either return never, or can return a new address to continue executing from when the handler is over