PearPackageFileSet enhancement

Hello,

On my way to find a way to add task replacements at pear packaging time only, I was sad with the PEAR_Task common task that implied to install additionnal task.

Because I wanted to have something equal to my custom PEAR task [1] but without the need to install it, I have a look on existing components of phing, and found the PearPackageFileSet type. 

So I've decided to improve its features and add : 

- auto detection of a pear local installation  (when using the config attribute )
- include / exclude pattern support  
- make the unit tests windows compatible

With this PR, I have the definitve solution to make my pear package (with PearPackage2Task) and apply the Git RCS keywords replacements at packaging time only (with this PearPackageFileSet type), and any other tasks I want to apply to my package filelist. 

Enjoy !
- Laurent

[1] https://github.com/llaville/pear-task-gitrcskeywords