rexml: Fix XPath bug of /#{ELEMENT_NAME}

It doesn't mean that all elements which name "ELEMENT_NAME" with any
namespace URI including null namespace URI. It means that all elements
which name "ELEMENT_NAME" with null namespace URI.

https://www.w3.org/TR/1999/REC-xpath-19991116/#NT-NodeTest

> if the QName does not have a prefix, then the namespace URI is null
> (this is the same way attribute names are expanded).

We need to use "*[local-name()='#{ELEMENT_NAME}']" for all elements
which name "ELEMENT_NAME" with any namespace URI including null
namespace URI in XPath 1.0. But it's inconvenient. So this change
includes "*:#{LOCAL_NAME}" syntax support that is introduced since
XPath 2.0.

* lib/rexml/parsers/xpathparser.rb: Support "*:#{LOCAL_NAME}" syntax that
  is introduced since XPath 2.0.

* lib/rexml/xpath_parser.rb:
  * Fix namespace URI processing for "#{ELEMENT_NAME}". Now,
    "#{ELEMENT_NAME}" doesn't accept elements with null namespace URI.
  * Add "*:#{LOCAL_NAME}" support.

* test/rexml/test_contrib.rb,
  test/rexml/test_core.rb,
  test/rexml/xpath/test_base.rb: Follow this change.

* test/rexml/test_jaxen.rb: Fix namespace processing.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63236 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rexml/parsers/xpathparser.rb

@@ -271,10 +271,12 @@ module REXML
       #   String, if a name match
       #NodeTest
       #  | ('*' | NCNAME ':' '*' | QNAME)                NameTest
-      #  | NODE_TYPE '(' ')'                              NodeType
+      #  | '*' ':' NCNAME                                NameTest since XPath 2.0
+      #  | NODE_TYPE '(' ')'                             NodeType
       #  | PI '(' LITERAL ')'                            PI
       #    | '[' expr ']'                                Predicate
-      NCNAMETEST= /^(#{NCNAME_STR}):\*/u
+      PREFIX_WILDCARD = /^\*:(#{NCNAME_STR})/u
+      LOCAL_NAME_WILDCARD = /^(#{NCNAME_STR}):\*/u
       QNAME     = Namespace::NAMESPLIT
       NODE_TYPE  = /^(comment|text|node)\(\s*\)/m
       PI        = /^processing-instruction\(/
@@ -282,6 +284,13 @@ module REXML
         original_path = path
         path = path.lstrip
         case path
+        when PREFIX_WILDCARD
+          prefix = nil
+          name = $1
+          path = $'
+          parsed << :qname
+          parsed << prefix
+          parsed << name
         when /^\*/
           path = $'
           parsed << :any
@@ -301,7 +310,7 @@ module REXML
           end
           parsed << :processing_instruction
           parsed << (literal || '')
-        when NCNAMETEST
+        when LOCAL_NAME_WILDCARD
           prefix = $1
           path = $'
           parsed << :namespace