Make FrameworkField ctor public. Fixes #1668

Prior to this change, custom runners could make `FrameworkMethod`
instances, but not `FrameworkField` instances. This small change
allows for both now, because `FrameworkField`'s constructor has been
promoted to `public` from package-private.

src/main/java/org/junit/runners/model/FrameworkField.java

@@ -15,6 +15,11 @@
 public class FrameworkField extends FrameworkMember<FrameworkField> {
     private final Field field;
 
+    /**
+     * Returns a new {@code FrameworkField} for {@code field}.
+     *
+     * Access relaxed to {@code public} since version 4.14.
+     */
     FrameworkField(Field field) {
         if (field == null) {
             throw new NullPointerException(
@@ -26,7 +31,7 @@ public class FrameworkField extends FrameworkMember<FrameworkField> {
             // This field could be a public field in a package-scope base class
             try {
                 field.setAccessible(true);
-            } catch (SecurityException  e) {
+            } catch (SecurityException e) {
                 // We may get an IllegalAccessException when we try to access the field
             }
         }