#2185 Automatic unpacking should not run on files with no equivalents

[pda]

WinMerge 2.14.0 on Windows

With Automatic Unpacking active, comparing directories will invoke automatic unpacking on entries which are unique to one directory only. This wastes enormous amounts of processing power and makes comparing two directories wich only have limited files in common very slow.

In general, if a file exists in one directory only, it should be skipped as soon as possible when comparing.