Rename builder esprima fixtures to babel

f724ae98a1 changed the build
script to use Babel, so this commit updates the file names accordingly

external/builder/fixtures_babel/comments.js

@@ -0,0 +1,26 @@
+/* globals f0 */
+function f1() {
+  /* head */
+  "1";
+  /* mid */
+  "2";
+  /* tail */
+}
+
+function f2() {
+  // head
+  "1";
+  // mid
+  "2";
+  // tail
+}
+
+function f3() {
+  if ("1") { // begin block
+    "1";
+  }
+  "2"; // trailing
+  if (/* s */"3"/*e*/) {
+    "4";
+  }
+}