Fractional GuiFont point sizes aren't preserved

[andrew-vant]

If I run (for example) GuiFont Monospace h10.5, it works fine at first; the result is visibly larger than h10, smaller than h11. However, if I read back the GuiFont afterward, it returns Monospace h11, as if it were rounded up. Normally that causes no issue...until I move the window to another screen, at which point the displayed font size gets reset to the rounded-up h11 value instead of preserving the h10.5 I actually set.

If I use h10.4 instead of h10.5, it gets rounded down to 10, and the rounded-down value is again applied when I move the window to another screen.

I know nothing about fonts or about nvim-qt's internals, so I'm not sure what the correct behavior is. I suspect nvim-qt does some magic to handle fractional point sizes when setting GuiFont, but stores the value in an int, so that magic doesn't happen when some later event reads it.