Bug 1432410 - Add tests in tree to make sure we don't regress with clang-tidy on static-analisys. Tests wrote in part by :sylvestre. r=gps

MozReview-Commit-ID: IWxzKfWNIHG

tools/clang-tidy/test/modernize-use-nullptr.cpp

@@ -0,0 +1,5 @@
+#define NULL 0
+void f(void) {
+  char *str = NULL; // ok
+  (void)str;
+}