hgview #137588 Use PyQt4 new coding style [done]

PyQt4 have 2 coding styles old-style and new-style.

Using the new-style is more pythonic than the old-style, it helps caching errors, it is python3 compatible, and it can help switching to PySide.

This requires to adapt Qt object api (version 2) and signal/slot.

See this interesting web site

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patch[qt] make pylint a little more happy [applied][qt4] use new signal coding-style [rejected][qt4] use new signal coding-style [applied]