Move Linux/Tru64 architecture independent code into kern/*

Move Linux/Tru64 architecture independent code into kern/*
leaving dependent code making way  for solaris linux syscall emu.

SConscript:
    Add two new files for syscall emulation
    Add getDesc() function
arch/alpha/alpha_linux_process.cc:
arch/alpha/alpha_tru64_process.cc:
    move architecture independent code into kern/linux/linux.(hh|cc)
arch/alpha/alpha_linux_process.hh:
arch/alpha/alpha_tru64_process.hh:
    Add getDesc function
kern/linux/linux.hh:
    move generi linux syscall emulation code into kern/linux
kern/tru64/tru64.hh:
    move generi tru64 syscall emulation code into kern/tru64
sim/process.cc:
sim/process.hh:
    Push the function determination and calling stuff down to LiveProcess
    and out of the Linux/Tru64 classes respectively
sim/syscall_emul.cc:
sim/syscall_emul.hh:
    fnctl implementation was identical in tru64 and linux so moved to generic

--HG--
extra : convert_revision : 103293dbe6fe2f7892de4929d17dc085def77026