tests: Add Unit tests for wl_map and wl_array data structures

We use a simple test-runner helper that runs each test in a separate
process and reports the pass/fail rate at the end.

tests/test-runner.h

@@ -0,0 +1,14 @@
+struct test {
+	const char *name;
+	void (*run)(void);
+};
+
+#define TEST(name)						\
+	static void name(void);					\
+								\
+	const struct test test##name			\
+		 __attribute__ ((section ("test_section"))) = {	\
+		#name, name					\
+	};							\
+								\
+	static void name(void)