Log Message:
Update to 6.3.1:

Version 6.3.1 - August 11 2014

[CHANGES]
New facilities:
o gtags.vim: New 'Gtagsa' (Gtags with append) command.
  This command appends tags to the current tag list.
  If you want to get a union of 'global -d foo' and
  'global -r foo' then please do as follows:

    :Gtags -d foo
    :Gtagsa -r foo

o geco.rc: New command (Bash function).
  You need bash, percol and less to use geco.

    $ source /usr/local/share/gtags/geco.rc
    $ geco --help       # show help
    $ geco mai[TAB]     # auto completion
              v
    $ geco main [ENTER]
    QUERY> init         # narrowing down
    (less's screen)
    :tag -r main        # tag jump again

    The same options are available on the both prompts:
    $ geco <options> arg
    :tag <options> arg

[INCOMPATIBLE CHANGES]
o global: The following configuration variables were removed
  since they will surely cause confusion.
  GTAGSROOT, GTAGSDBPATH