Source code incompatible regression in QScopedArrayPointer

change 746114fb8a1036e5ccec88fe22e9378925d3a34a adds a regression to 4.7. The
following code doesn't compile any more (it did compile with 4.7):

QScopedArrayPointer<char> foo;

Suggestion: Either fix the templates to accept the default "= 0" parameter as
valid input, or add a new default constructor that does not take any
arguments.