cmd/objdump: actually accept hex address without "0x" prefix. Fixes issue 7936.
cmd/objdump: actually accept hex address without "0x" prefix.
Fixes issue 7936.

LGTM=alex.brainman, bradfitz, iant
R=golang-codereviews, alex.brainman, bradfitz, iant
CC=golang-codereviews
https://codereview.appspot.com/100060043

bryanxu/go-zh,bryanxu/go-zh,d0f/go-zh,bryanxu/go-zh,webfd/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,d0f/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,d0f/go-zh,webfd/go-zh,bryanxu/go-zh,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,sanjosh/sanjos100-tipc,bryanxu/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,d0f/go-zh,d0f/go-zh,d0f/go-zh,webfd/go-zh,sanjosh/sanjos100-tipc,webfd/go-zh,webfd/go-zh,bryanxu/go-zh,bryanxu/go-zh