Also fixes a few cases where URL1's data (like start pos)
was leaking into URL2
function old new delta
wget_main 2303 2321 +18
progress_meter 140 152 +12
retrieve_file_data 397 396 -1
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(add/remove: 0/0 grow/shrink: 2/1 up/down: 30/-1) Total: 29 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>