Genie:  Return the number from enter_system_call()
Genie:  Don't restore D0 after enter_system_call()
Genie:  Restore r11 from r3, not the stack
Merge branch 'return-syscall-number'
Genie -> relix:  Move breathe() declaration
Genie -> relix:  Move pump() system call
Genie:  Fix link.cc header comment
Genie:  Axe unused SystemCallRegistry.hh include
Genie:  Axe unused GetSystemCall()