Can't set fontsize for stationplot symbol plot

[dopplershift]

fig, ax = plt.subplots(dpi=300)
sp = StationPlot(ax, [0], [0], fontsize=8, spacing=32)
sp.plot_symbol('W', [96], current_weather, fontsize=36)

Doesn't produce the expected large thunderstorm symbol. This is because in plot_symbol, we pass:

        kwargs['fontproperties'] = wx_symbol_font

later in the matplotlib code for Text, the FontProperty instance is modified in place. Instead, that should be:

        kwargs['fontproperties'] = wx_symbol_font.copy()

[jrleeman]

Cannot reproduce, example works with current master.

[dopplershift]

This reproduces:

fig, ax = plt.subplots(dpi=300)
sp = StationPlot(ax, [0], [0], fontsize=8, spacing=32)
sp.plot_symbol('E', [92], current_weather)
sp.plot_symbol('W', [96], current_weather, fontsize=36)