top: switch to malloced "globals".

top: switch to malloced "globals".

This seems to be more efficient:

function                                             old     new   delta
clearmems                                              -      28     +28
display_process_list                                1001    1018     +17
read_cpu_jiffy                                       171     177      +6
do_stats                                             194     198      +4
reset_term                                            20      23      +3
topmem_sort                                           63      65      +2
mult_lvl_cmp                                          44      45      +1
get_jiffy_counts                                     247     248      +1
display_topmem_process_list                          549     546      -3
top_main                                             912     879     -33
handle_input                                         630     549     -81
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 7/3 up/down: 62/-117)           Total: -55 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>