Log a warning if an execution block of a target is reassigned.


git-svn-id: http://sbuild.tototec.de/svn/sbuild/trunk@365 024a02f7-42f7-40fc-9f58-65666d1f2450
Added new ThreadLocal WithinTargetExecution holding the TargetContext. 
Added two new apply methods to IfNotUpToDate utilizing newly added WithinTargetExecution.


git-svn-id: http://sbuild.tototec.de/svn/sbuild/trunk@366 024a02f7-42f7-40fc-9f58-65666d1f2450
Improved error messages.


git-svn-id: http://sbuild.tototec.de/svn/sbuild/trunk@367 024a02f7-42f7-40fc-9f58-65666d1f2450
Added API usage guards to TargetRef.files and TargetRefs.files, which should only be called from inside a targets exec block, in preparation for support for attached files.


git-svn-id: http://sbuild.tototec.de/svn/sbuild/trunk@368 024a02f7-42f7-40fc-9f58-65666d1f2450
Extended API of TargetContext by preprequisitesLastModified and attachFile.


git-svn-id: http://sbuild.tototec.de/svn/sbuild/trunk@369 024a02f7-42f7-40fc-9f58-65666d1f2450