Redrawn antialiased characters become bolder

[Anders Kaseorg]

When using emacs-snapshot-gtk 1:20080228-1 in hardy with antialiased
fonts, characters often become distractingly bolder when they are
redrawn.

In this screenshot, I typed a line of text twice.  After typing the
second line, I moved to the beginning of the line, then moved right
character by character to the end.  This causes the second line to be
redrawn without being erased, so it ends up bolder than the first:

<http://foo.kaseorg.com/~anders/emacs-redrawn-characters.png>

Anders