This change is not backward compatible unfortunately. The format of
the gnome-session .session files has changed, such that every part
of the session is now listed on the RequiredComponents line.

When the strict option is used, normal windows are not able to show themselves
while showing the desktop.

Original commit messages:
. Reformat to move closer to house style
. Add center on top of leat overlap place algo
. Add sentinel value to edge arrays
. Use a Size instead of a Rect for a centering field
. Fix off by one bug
. Need to declare dx and dy
. Pass length of edge array instead of recomputing
. Fix missing open-brace in config.c
. Address the more trivial subset of danakj comments
. Revert "Remove now-unused config_place_center option."
  This reverts commit 5e282dae08be3b900e0337efa0fae8f3ffa92cd7.
. Remove reliance on sentinel value when scanning edge arrays
. Avoid need to initialize Size structure by removing it :)
. Clean up field expansion code somewhat
. Compress code further by using a structure for common args
. Fix search for next grid point
. Squeeze it even more by not using Size at all

Use the following in your per-app rules:

<size>
  <width>A</width>
  <height>B</height>
</size>

A and B can be integer values to specify a size in pixels. They can also be
percentages or fractions to be relative to the size of the monitor the window
is placed on.

The new LeastOverlap placement doesn't use this option, and it kind of defeats
the purpose of the algorithm.

As stdout is redirected to /dev/null by some DMs, we need to print error
messages to stderr.