What to do with setup_{host, target, build}_hook and cleanup_target_hook procedures?

[Jacob Bachmeyer]

First, some of the behavior that I will be documenting for loading 
testsuite configuration (which is on the "testsuite" side of DejaGnu) is 
actually implemented in setup_target_hook, which is a customization 
point on the "testing lab" side of DejaGnu.  Similarly, the call to 
${tool}_exit is actually in cleanup_target_hook, with the same problem 
-- behavior on which testsuites should be able to rely is conflated with 
test lab customization points.

Second, the setup_*_hook procedures all set internal variables that test 
lab configuration should not have to worry about.

Third, there is a cleanup_target_hook, but no cleanup hooks for host or 
build.  This is an odd asymmetry.

I propose:
   1.  Add cleanup_{build,host}_hook procedures.
   2.  Ensure that all *_hook procedures are empty and move all 
framework-related code to new procedures.

Most sites that simply install DejaGnu and run tests locally should be 
unaffected by these changes.  I suspect that even most sites that have 
global configuration files probably are not overriding the *_hook 
procedures and will also not be affected.  Those few sites that will be 
affected by this are presumably run by people who will notice the item 
in NEWS that default processing for *_hook procedures has been moved 
elsewhere and adjust their configurations accordingly.


-- Jacob