Changed TestRunner.sh to dump the output and generated script files in

Changed TestRunner.sh to dump the output and generated script files in
subdirectories mirroring where the test case file is located

For example, for the test case "Sema/stmt_exprs.c", instead of the files
"Output/stmt_exprs.c.out" and "Output/stmt_exprs.c.out.script" being created, the
files "Output/Sema/stmt_exprs.c.out" and "Output/Sema/stmt_exprs.c.out.script" are
created. This prevents any collisions from different test directories that have the
same file name for a test case, and also makes it clear where the test case was
drawn from.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@44410 91177308-0d34-0410-b5e6-96231b3b80d8