Changelog from 0.7.2 to 0.7.4:

the 0.7.2 series overlay came from Bug 210428.

Changes:
-------

emerald-0.7.4 comes from source being patched with the
urefd.patch already ---> took it out.

mutual dependencies between the packages of this compiz-series 
were often stated with explicite reference to the version number
---> replaced those with the ${PV} statement.

compiz-bcop was suggested (Bug 197284) to be moved from 
x11-libs to dev-util ---> well, why not. done that!

let the dependency on libxcb of package compiz depend on 
the xcb 'USE' flag: ---> xcb? ( x11-libs/libxcb )