libbb: get rid of statics in dump.c; code shrinks a lot too

libbb: get rid of statics in dump.c; code shrinks a lot too

function                                             old     new   delta
alloc_dumper                                           -      26     +26
hexdump_main                                         600     601      +1
static.done                                            1       -      -1
static.ateof                                           1       -      -1
bb_dump_vflag                                          1       -      -1
static.savp                                            4       -      -4
static.nextfs                                          4       -      -4
static.curp                                            4       -      -4
exitval                                                4       -      -4
endfu                                                  4       -      -4
bb_dump_length                                         4       -      -4
bb_dump_fshead                                         4       -      -4
bb_dump_blocksize                                      4       -      -4
_argv                                                  4       -      -4
bb_dump_add                                          365     358      -7
savaddress                                             8       -      -8
eaddress                                               8       -      -8
bb_dump_skip                                           8       -      -8
address                                                8       -      -8
bb_dump_dump                                        2748    2672     -76
next                                                 538     445     -93
------------------------------------------------------------------------------
(add/remove: 1/16 grow/shrink: 1/3 up/down: 27/-247)         Total: -220 bytes
   text	   data	    bss	    dec	    hex	filename
 789458	    607	   6764	 796829	  c289d	busybox_old
 789309	    601	   6696	 796606	  c27be	busybox_unstripped