Support visibility modifiers in namespaced names

Fixes #704.

lib/PhpParser/Lexer.php

@@ -494,6 +494,7 @@ class Lexer
         // Based on semi_reserved production.
         return array_fill_keys([
             \T_STRING,
+            \T_STATIC, \T_ABSTRACT, \T_FINAL, \T_PRIVATE, \T_PROTECTED, \T_PUBLIC,
             \T_INCLUDE, \T_INCLUDE_ONCE, \T_EVAL, \T_REQUIRE, \T_REQUIRE_ONCE, \T_LOGICAL_OR, \T_LOGICAL_XOR, \T_LOGICAL_AND,
             \T_INSTANCEOF, \T_NEW, \T_CLONE, \T_EXIT, \T_IF, \T_ELSEIF, \T_ELSE, \T_ENDIF, \T_ECHO, \T_DO, \T_WHILE,
             \T_ENDWHILE, \T_FOR, \T_ENDFOR, \T_FOREACH, \T_ENDFOREACH, \T_DECLARE, \T_ENDDECLARE, \T_AS, \T_TRY, \T_CATCH,

test/code/parser/expr/keywordsInNamespacedName.test

@@ -9,6 +9,7 @@ namespace static;
 fn\use();
 \fn\use();
 namespace\fn\use();
+private\protected\public\static\abstract\final();
 -----
 !!php7
 array(
@@ -92,6 +93,22 @@ array(
                     )
                 )
             )
+            3: Stmt_Expression(
+                expr: Expr_FuncCall(
+                    name: Name(
+                        parts: array(
+                            0: private
+                            1: protected
+                            2: public
+                            3: static
+                            4: abstract
+                            5: final
+                        )
+                    )
+                    args: array(
+                    )
+                )
+            )
         )
     )
 )