[REG 4.8.7->5.6.1] QFontMetricsF reports incorrect width for strings containing zero-width unicode characters

Strings that contain sequences of ZWNJ (0x200c) or ZWSP (0x200b) cause QFontMetricsF to report boundingRects that do not match QPainter. In Qt 4 (4.8.7), the attached program outputs

|.| QRectF(-24,-1237 444x1571)
|..| QRectF(-24,-1237 444x1571)
|...| QRectF(-24,-1237 444x1571)

|*| QRectF(0,-1237 444x1571)
|**| QRectF(0,-1237 444x1571)
|***| QRectF(0,-1237 444x1571)

which correctly reflects the fact that repeated ZWNJ and ZWSP do not add actual width to text. In Qt5 (5.6.1), however, the output is:

|.| QRectF(0,-1237 814x1571)
|..| QRectF(0,-1237 1184x1571)
|...| QRectF(0,-1237 1554x1571)

|*| QRectF(0,-1237 868x1571)
|**| QRectF(0,-1237 1292x1571)
|***| QRectF(0,-1237 1716x1571)

This is not correct, and does not match how Qt renders text containing ZWNJ and ZWSP.