[NtUser] Fix maximizing to window edge

Cover up the edge of the frame while maximizing the window to desktop.
Fixes CORE-15893.

Author: jimtabor

win32ss/user/ntuser/winpos.c

@@ -958,6 +958,10 @@ co_WinPosGetMinMaxInfo(PWND Window, POINT* MaxSize, POINT* MaxPos,
 
     adjust = IntGetWindowBorders(adjustedStyle, exstyle);
 
+    // Handle special case while maximized. CORE-15893
+    if ((adjustedStyle & WS_THICKFRAME) && !(adjustedStyle & WS_CHILD) && !(adjustedStyle & WS_MINIMIZE))
+         adjust += 2;
+
     xinc = yinc = adjust;
 
     if ((adjustedStyle & WS_THICKFRAME) && (adjustedStyle & WS_CHILD) && !(adjustedStyle & WS_MINIMIZE))