Fix regression on cursor controls at last column

Commit 8de0e6c7 mistakenly removed code to cancel the pending wrap flag
(which in konsole is implemented as having the cursor one past the width
of the screen) before the cursor controls CUU, CUD, CUB and BS.

While the behavior may seem counter-intuitive (specially BS and CUB,
where `printf "A\bB"` at the last column results in `BA`), this is the
behavior of VT100, xterm (without reverse-wraparound mode), and, most
importantly, is expected by ncurses.

CCBUG: 399615

src/Screen.cpp

@@ -96,6 +96,7 @@ void Screen::cursorUp(int n)
         n = 1; // Default
     }
     const int stop = _cuY < _topMargin ? 0 : _topMargin;
+    _cuX = qMin(_columns - 1, _cuX); // nowrap!
     _cuY = qMax(stop, _cuY - n);
 }
 
@@ -109,6 +110,7 @@ void Screen::cursorDown(int n)
         n = MAX_SCREEN_ARGUMENT;
     }
     const int stop = _cuY > _bottomMargin ? _lines - 1 : _bottomMargin;
+    _cuX = qMin(_columns - 1, _cuX); // nowrap!
     _cuY = qMin(stop, _cuY + n);
 }
 
@@ -118,6 +120,7 @@ void Screen::cursorLeft(int n)
     if (n < 1) {
         n = 1; // Default
     }
+    _cuX = qMin(_columns - 1, _cuX); // nowrap!
     _cuX = qMax(0, _cuX - n);
 }
 
@@ -768,6 +771,7 @@ void Screen::reset()
 
 void Screen::backspace()
 {
+    _cuX = qMin(_columns - 1, _cuX); // nowrap!
     _cuX = qMax(0, _cuX - 1);
 
     if (_screenLines.at(_cuY).size() < _cuX + 1) {