Fix QSettings problems: - Reopen file in ReadOnly mode if it was open in ReadWrite mode and is being read. This is needed for stupid QSettings which opens file in ReadWrite mode just to call readAll() on it. - Implement setSize(0)

[patterns]
**.h = native
**.c = native
**.cpp = native
**.lua = native
**.txt = native
**.pas = native
**.inc = native
**.hs = native