IDE: refactor functions that build Lazarus. Make them a class. Reduces func parameters and makes changes later easier.

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43977 4005530d-fff6-0310-9dd1-cebe43e6787f
Packager: refactor, remove a parameter from PackageGraph.GetIDEInstallPackageOptions.

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43978 4005530d-fff6-0310-9dd1-cebe43e6787f
LazBuild: make changes required by the earlier refactoring.

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43979 4005530d-fff6-0310-9dd1-cebe43e6787f
Revert r43941 "LCL: take PageSize into account when calculating ScrollBar position. Issue #20127"

git-svn-id: http://svn.freepascal.org/svn/lazarus/trunk@43980 4005530d-fff6-0310-9dd1-cebe43e6787f