Added preprocessor tests

test/basic/check_success/preprocess.cvc

@@ -0,0 +1,5 @@
+#include "civic.h"
+
+export int main() {
+    return 0;
+}

test/basic/functional/preprocess.cvc

@@ -0,0 +1,9 @@
+#include "civic.h"
+
+export int main() {
+    printInt(1);
+    printNewlines(1);
+    printFloat(2.0);
+    printNewlines(1);
+    return 0;
+}