tests: link them dynamically by default

. so that functionality is tested
	. add test63 that actually tests dlopen(), dlsym(),
	  etc. functionality; only built if clang supports it
	. also test10 test to copy more of the executable

test/mod.c

@@ -0,0 +1,27 @@
+
+/* Code for module to be loaded by test63. */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <dlfcn.h>
+
+#include "magic.h"
+
+long cookie = 0;
+
+void exithandler(void);
+
+long modfunction(long v1, long *argcookie, long v2) {
+  if(v1 != MAGIC4 || v2 != MAGIC5) {
+	fprintf(stderr, "wrong args to modfunction\n");
+	exit(1);
+  }
+  *argcookie = MAGIC3;
+  cookie = MAGIC2;
+  atexit(exithandler);
+  return MAGIC1;
+}
+
+void exithandler(void) {
+	/* OK */
+}