Compile LuaJIT with LUAJIT_USE_PERFTOOLS and LUAJIT_USE_GDBJIT.

These are valuable debugging tools and they have no immediately
obvious performance impact.

Particularly useful is LUAJIT_USE_PERFTOOLS so that Linux 'perf top'
will show individual traces.
Use the "zone" feature for LuaJIT profiling.

Snabb Switch now tells the profiler what "zone" of computation is
executing at any given time. The profiler is then able to report on
each zone separately, when given the -jp=z flag.

The zone name for an app can be given explicitly as the "zone" field
of the app (or its class). If no name is given then one is guessed
based on the module name of the app's code.

Example output:

    # ./snabbswitch -jp=2zF -t apps.intel.intel_app
    75%  apps.intel.intel_app
      -- 18%  intel10g.lua:transmit < intel_app.lua:push
      -- 17%  intel10g.lua:receive < intel_app.lua:pull
      -- 11%  buffer.lua:free < packet.lua:free
      --  7%  intel10g.lua:sync_transmit < intel_app.lua:push
      --  5%  intel10g.lua:can_add_receive_buffer < intel_app.lua:add_receive_buffers
      --  4%  register.lua:RDH < intel10g.lua:sync_receive
      --  3%  freelist.lua:add < buffer.lua:free
      --  3%  intel10g.lua:add_receive_buffer < intel_app.lua:add_receive_buffers
      --  3%  link.lua:receive < intel_app.lua:push
      --  3%  link.lua:transmit < intel_app.lua:pull
      --  3%  freelist.lua:remove < packet.lua:allocate
    11%  Sink
      -- 48%  buffer.lua:free < packet.lua:free
      -- 13%  freelist.lua:add < packet.lua:free
      -- 11%  link.lua:receive < basic_apps.lua:push
      --  9%  freelist.lua:add < buffer.lua:free
      --  7%  packet.lua:free < packet.lua:deref
      --  7%  packet.lua:deref < basic_apps.lua:push
    10%  Source
      -- 45%  packet.lua:add_iovec < basic_apps.lua:pull
      -- 15%  link.lua:transmit < basic_apps.lua:pull
      -- 15%  freelist.lua:remove < buffer.lua:allocate
      -- 11%  link.lua:full < link.lua:transmit
      --  8%  freelist.lua:remove < packet.lua:allocate
      --  6%  basic_apps.lua:pull < app.lua:breathe
     4%  selftest
      -- 27%  lib.lua:waitfor < register.lua:wait
      -- 27%  memory.lua:allocate_RAM < memory.lua:allocate_next_chunk
      -- 23%  app.lua:breathe < app.lua:main
      -- 14%  zone.lua:zone < app.lua:breathe
      --  5%  lib.lua:firstline < pci.lua:device_info
      --  5%  lib.lua:done < app.lua:main
Merge pull request #140 from lukego/debug

Debug: Enable more LuaJIT features for debugging