Fix improper XHPAST parsing of namespace grammar like "use x as private;"

Summary:
Depends on D21067. Ref T13492. Converting unit tests to be readable exposed this error in the grammar.

Normally, "grammar_rule" rules emit a standalone Node. In this case, the bottom-level grammar rule is a collection of trivial rules and the callers configure the Node. Wrap the bottom-level rule in a configuration rule so the node is configured correctly and consistently, in exactly one place.

Test Plan: Ran unit tests.

Maniphest Tasks: T13492

Differential Revision: https://secure.phabricator.com/D21068

src/parser/xhpast/__tests__/data/php-traits.php.test

@@ -205,7 +205,7 @@ pass
         > " "
         > as
         > " "
-        * "<INVALID TYPE \"0\">"
+        * n_STRING
          > protected
         * n_EMPTY
        > " "

src/parser/xhpast/bin/PhutilXHPASTBinary.php

@@ -8,7 +8,7 @@ final class PhutilXHPASTBinary extends Phobject {
    * This is the version that would be obtained with an up-to-date XHPAST
    * build. The //actual// XHPAST build version may vary.
    */
-  const EXPECTED_VERSION = '7.1.5';
+  const EXPECTED_VERSION = '7.1.6';
 
   /**
    * The XHPAST build version.

support/xhpast/parser.y

@@ -1335,7 +1335,7 @@ trait_modifiers:
   }
 |  member_modifier  {
     $$ = NNEW(n_METHOD_MODIFIER_LIST);
-    $$->appendChild(NTYPE($1, n_STRING));
+    $$->appendChild($1);
   }
 ;
 
@@ -1370,14 +1370,20 @@ method_modifiers:
 non_empty_member_modifiers:
   member_modifier {
     $$ = NNEW(n_CLASS_MEMBER_MODIFIER_LIST);
-    $$->appendChild(NTYPE($1, n_STRING));
+    $$->appendChild($1);
   }
 | non_empty_member_modifiers member_modifier {
-    $$ = $1->appendChild(NTYPE($2, n_STRING));
+    $$ = $1->appendChild($2);
   }
 ;
 
 member_modifier:
+  basic_member_modifier {
+    $$ = NTYPE($1, n_STRING);
+  }
+;
+
+basic_member_modifier:
   T_PUBLIC
 | T_PROTECTED
 | T_PRIVATE