wget: notify on download begin and end

wget: notify on download begin and end

When using -o to file the progress meter is not displayed, so write that
we started the download and that we finished it.

function                                             old     new   delta
retrieve_file_data                                   465     561     +96
wget_main                                           2412    2432     +20
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 116/0)             Total: 116 bytes
   text	   data	    bss	    dec	    hex	filename
 979022	    485	   7296	 986803	  f0eb3	busybox_old
 979224	    485	   7296	 987005	  f0f7d	busybox_unstripped

Signed-off-by: Martin Lewis <martin.lewis.x84@gmail.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>