[CMake] [ANN] New PkgConfig module

[Bill Hoffman]

frederic heem wrote:
> I've modified UsePkgConfig too.
> The reasons why it has been modified is that it allows to search on non 
> standard pkg path. It also retrieves the package version and the definitions
> It should be nice to merge all work done.
> Frederic Heem
>   
I just want to make sure it is all backwards compatible with current 
releases of cmake.

-Bill