Windows dbghelp strips leading underscores from symbols, so let's accept "ZN...E" form too.
Also, print PC displacement from symbols.
Fix typo
auto merge of #19819 : vadimcn/rust/fix-demangle, r=alexcrichton

Windows dbghelp strips leading underscores from symbols, and I could not find a way to turn this off.  So let's accept  "ZN...E" form too.
Also, print PC displacement from symbols.  This is helpful in gauging whether the PC was indeed within the function displayed in the backtrace, or whether it just happened to be the closest public symbol in the module.