Fix issues with code interlock in generic mode

There was a missing \csname here which hid a number of problems. The grouping
needed altering so that \PackageError is defined where needed. This is all
now working.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4781 de43f980-851b-0410-b2f7-c40aca1f87e0
Fix error message given in generic mode if required primitives not available

As with the previous checkin, the issue here is getting the grouping correct.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4782 de43f980-851b-0410-b2f7-c40aca1f87e0