We only have one syscall table: inline sysent/SYS_MAXSYSCALL and

We only have one syscall table: inline sysent/SYS_MAXSYSCALL and
SYS_syscall as the nosys() function into the MD syscall entry
routines and the SYSCALL_DEBUG support.  Adjust alpha's syscall
check to match the other archs.  Also, make sysent const to get it
into .rodata.

With that, 'struct emul' is unused: delete it and all its references

ok millert@