reworked pptest1/4/5 into executable tests and moved to test/val

test/val/pptest1.c

@@ -0,0 +1,27 @@
+
+/* preprocessor test #1 */
+
+#define hash_hash       # ## #
+#define mkstr(a)        # a
+#define in_between(a)   mkstr(a)
+#define join(c, d)      in_between(c hash_hash d)
+
+#define x "first"
+#define y "second"
+
+char p[] = join(x, y);          // Comment
+
+#include <string.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+int main(void)
+{
+    printf("expected: %s\n", "\"first\" ## \"second\"");
+    printf("p:        %s\n", p);
+    if (!strcmp(p, "\"first\" ## \"second\"")) {
+        return EXIT_SUCCESS;
+    }
+    printf("all fine\n");
+    return EXIT_FAILURE;
+}