Add a symbolic link from the test directory to the actual - elsewhere located...

Add a symbolic link from the test directory to the actual - elsewhere located - path that contains the test cases - and teach the test suite driver to resolve paths that contain symbolic links to test cases

This is meant to reduce the typing that one needs to do to get from the test subdirectory to actual test cases. Now one can just do

$ ./dotest.py ./testcases/<yaddayaddayadda>

llvm-svn: 255741