Strings containing zero-width spaces may be rendered incorrectly

The attached test case displays the string "+0f-1", where a zero-width space character (QChar(0x200b)) is inserted between '0' and 'f', on screen in a QLabel. The characters 'f' and '1' are swapped, such that the label reads "+01-f". If the zero-width space is removed, the string is displayed correctly.

Tested using a recent checkout of the 4.7 branch on Linux (OpenSuse).