Outward ticks cause labels to be clipped by default

[QuLogic]

In the unicode demo, text in the xlabel is clipped because the outward ticks push the label down:

In 1.5.2, this works fine by default:

This example doesn't use tight_layout, but there is nothing complicated here (just a single Axes) and I think it should be handled correctly by default.

[overdetermined]

Interestingly, I had this problem frequently in version 1.5.1.

[QuLogic]

Just as a note that this is not caused by the accented characters, here is another demo that clips the labels.

[mdboom]

The best fix is probably to move in the axes margins on all four sides. The title at the top will still be too close, however, so there'll be some other fix needed there.

[jenshnielsen]

This should be fixed by #6468

[efiring]

closed by #6468