Simplifying Piecewise when two cases have same value

[cbm755]

In [92]: Piecewise((0, Eq(x, 0)), (sin(x), True))
Out[92]: Piecewise((0, x == 0), (sin(x), True))

In [93]: pprint(_)
⎧  0     for x = 0
⎨                 
⎩sin(x)  otherwise

In [94]: simplify(_)
Out[94]: Piecewise((0, x == 0), (sin(x), True))

Perhaps this should not happen automatically, but it would be nice if simplify() did it. Apologies if this is a dupe, didn't see it. Figure its related to #1009 somehow.

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Very simple cases work:

In [97]: Piecewise((10, Eq(x,0)), (10, True))
Out[97]: 10

And some more complicated things work too:

In [101]: p3 = Piecewise((10, Eq(x, 0)), (y, True))

In [101]: p3
Out[101]: Piecewise((10, x == 0), (y, True))

In [102]: p3.subs(y,10)
Out[102]: 10

[smichr]

cf #8453