Fixing the interpretation of $srcdir in DejaGnu

As part of the ongoing efforts to improve Automake integration, I have 
split the previously-conflated uses of $srcdir in DejaGnu.  Due to the 
current architecture of DejaGnu, the new variable created to hold the 
base directory of the testsuite ("@srcdir@/testsuite" using Automake's 
@srcdir@) is visible to test scripts.

At the moment that variable is named "testsuitedir" and may or may not 
have the same value as "srcdir".  The core uses it, but it could also be 
useful as a transitional feature in test scripts, since a script using 
this variable will work independently of using Automake's srcdir value 
or a legacy srcdir=@srcdir@/testsuite value.

Is "testsuitedir" the best name for this variable or can anyone suggest 
a better name, or possibly an API call to wrap it?  (Maybe something 
like "[testsuite file <name>...]" to refer to a file within the 
testsuite sources, equivalent to "[file join $testsuitedir <name>...]"?)

Interestingly, the DejaGnu procedure "getdirs" excludes directories 
named "testsuite" from recursive searches.  An alternative would be for 
this procedure to instead enter "testsuite" as its first step, but 
keeping the current behavior allows nested testsuites that use runtest 
recursively without having the outer runtest scan inner testsuites.  
This will be useful for the DejaGnu testsuite itself at a minimum.


-- Jacob