There are some bugs in the pkg-config files of the new extensions, which makes
it impossible to build for example metacity with compositor (without patching).
The following seds should fix that:
sed -i -e 's/Name: Xdamage/Name: Xcomposite/' xc/lib/Xcomposite/xcomposite.pc.in
sed -i -e 's/PACKAGE_VERSION/VERSION/'
Must have been a copy-and-paste error, fix committed.