Enhance test system

- Tests are now named
- Testlogs are preserved between runs
- Tests can be run through Valgrind Memcheck tool

test/test-invalid

@@ -1,20 +1,20 @@
 #!/bin/sh
 
 TESTFILES="${srcdir}/testdata/invalid ${srcdir}/testdata/invalid-unicode"
-TMPDIR="tmp"
 
 run_test() {
     local prog=$1
-    local input=$2
-    local output=$3
-    run_testprog $prog $TMPDIR/$input
-    if ! cmp $TMPDIR/$output $TMPDIR/error >/dev/null; then
-        echo "### $input ($prog) failed:" >&2
-        cat $TMPDIR/$input >&2
+    local prefix=$2
+
+    run_testprog $prog $prefix
+    if ! cmp $prefix.out $prefix.$prog.stderr >/dev/null; then
+        echo >&2
+        echo "### $prefix ($prog) failed:" >&2
+        cat $prefix.in >&2
         echo "### expected output:" >&2
-        cat $TMPDIR/$output >&2
+        cat $prefix.out >&2
         echo "### actual output:" >&2
-        cat $TMPDIR/error >&2
+        cat $prefix.$prog.stderr >&2
         exit 1
     fi
 }