It works if you alias the id, then it's just a normal GROUP BY on the first column (1) to get the sums

SELECT
   CASE WHEN num <= @row_limit THEN queue_name ELSE 'others' END name,
   num, queue_name, jobs_pend, jobs_run
FROM
  (
  SELECT
    @row_num := @row_num + 1 as num,
    queue_name, jobs_pend, jobs_run
  FROM
    queues, (SELECT @row_num := 0, @row_limit:=5) r
  ) q
[download]

gives

name          num   queue_name    jobs_pend jobs_run
adice_long     1    adice_long       5        39
adice_ncsim    2    adice_ncsim      0         6
adice_short    3    adice_short    254       192
calibre        4    calibre          0         0
dsp_ncsim_gls  5    dsp_ncsim_gls    0         2
others         6    dsp_ncsim_hp     0         2
others         7    dsp_ncsim_lp     0         5
others         8    dsp_ncsim_mp     0         5
others         9    hcg_ncsim_comp   0         0
others         10   hcg_ncsim_hp     0         9
others         11   hcg_ncsim_lp     0         0
others         12   hcg_ncsim_mp     0         0
others         13   hcg_ncsim_short  0         0
others         14   ipdc_pte         0         0
others         15   ncsim_long      41        78
others         16   ncsim_lp         1         4
others         17   ncsim_short      0        84
others         18   normal         170        30
others         19   spectreRF        0         1
others         20   vcs              0         0
[download]