- Add Verilog-2001 and Verilog-2005 keywords to filetypes.verilog
  (right now only Verilog-1995 keywords are highlighted).
  These keywords were already included in ctags.
- Add all System tasks and functions as of Verilog-2005 to `word2` list
  (right now only a handful appear; perhaps from an older standard).

Details on added/removed keywords:

Add new keywords from Verilog-2001 and Verilog-2005 standard (Annex B)
(right now only Verilog-1995 keywords are listed):

    automatic generate endgenerate genvar localparam uwire
    config endconfig cell design instance liblist use
    library incdir include
    pulsestyle_ondetect pulsestyle_onevent showcancelled noshowcancelled

Remove invalid Verilog keywords:

    attribute endattribute strength @

Put all "keywords used to declare nets/variables/constants/events"
in `word3` list; leave rest in `word`.

Add all functions/tasks listed under "System tasks and functions"
in the Verilog-2005 standard (chapter 17).