testsuite: Add basic mysql test case.

test/completion/mysql.exp

@@ -0,0 +1 @@
+assert_source_completions mysql

test/lib/completions/mysql.exp

@@ -0,0 +1,20 @@
+proc setup {} {
+    save_env
+}
+
+
+proc teardown {} {
+    assert_env_unmodified
+}
+
+
+setup
+
+
+assert_complete_any "mysql --"
+
+
+sync_after_int
+
+
+teardown