[Lazarus] Search paths per platform

[Hans-Peter Diettrich]

Sven Barth schrieb:

> 2. Delphi uses the Windows Registry to store its known packages, true, 
> but Lazarus basically does the same for its installed packages in its 
> XML files that are stored in e.g. %APPDATA%\lazarus or ~/.lazarus.

The difference becomes obvious with multiple Lazarus installations. 
Where multiple Delphi versions share packages (causing trouble), every 
Lazarus installation must be configured explicitly.

DoDi