Using Mark interferes with cursor positioning

[rprichard]

The fix for #53 switched the "freeze" technique from SelectAll to Mark for the new Windows 10 console. The rationale was that Mark didn't move the cursor in that mode, making it acceptable.

Unfortunately, it still does interfere in a way -- when the Mark command ends, the cursor is restored to its pre-Mark position, even if it has been moved in the meantime. This is causing noticeable problems in PowerShell and cmd.exe.

PowerShell:

When pressing Return, sometimes the prompt duplicates like this:

PS C:\rprichard\proj\winpty>
PS C:\rprichard\proj\winpty> PS C:\rprichard\proj\winpty>
PS C:\rprichard\proj\winpty> PS C:\rprichard\proj\winpty>

cmd.exe:

When tab completing choices, sometimes the line has junk at the end:

C:\>cd Intel ntel

Here's a test script useful for demonstrating the problem. Build misc/SetCursorPos.exe, then run the batch file, then start Mark or SelectAll:

@echo off
cls
echo 123
echo 123
echo 123
echo 123
echo 123
echo 123
ping -n 4 127.0.0.1 >NUL
SetCursorPos 0 0
ping -n 4 127.0.0.1 >NUL

[rprichard]

This bug was introduced in ce2d9f1, and it affects 0.2.0 and newer.