Fixes for replaying plots

[cpsievert]

Closes #39.

653640c seems sufficient for fixing the issue for grid graphics, but 13e252c also seems necessary to fix the issue for base graphics (I'm not entirely sure why the timing matters). Here's a minimal base example:

library(showtext)
font_add_google("Lobster", "lobster")
showtext_auto()
png("foo.png")
dev.control(displaylist = "enable")
plot(1, pch = 16, cex = 3)
text(1, 1.1, "A fancy dot", family = "lobster", col = "steelblue", cex = 3)
result <- recordPlot()
dev.off()
file.show("foo.png")

png("foo2.png")
replayPlot(result)
dev.off()
file.show("foo2.png")

[yixuan]

Thank you @cpsievert for your effort! Let me take a look at the code and see what to do next. I'll get you back soon.

[yixuan]

This patch looks great! I'll submit a new version in the next few days.