Bug#16320 XML: extractvalue() won't accept names containing underscores

  added '_' to allowed tag body symbols

mysql-test/r/xml.result

@@ -546,3 +546,6 @@ select extractvalue('<a>A</a>','/<a>');
 ERROR HY000: XPATH syntax error: '>'
 select extractvalue('<a><b>b</b><b!>b!</b!></a>','//b!');
 ERROR HY000: XPATH syntax error: '!'
+select extractvalue('<A_B>A</A_B>','/A_B');
+extractvalue('<A_B>A</A_B>','/A_B')
+A

mysql-test/t/xml.test

@@ -243,3 +243,8 @@ select extractvalue('<a>A</a>','/<a>');
 #
 --error 1105
 select extractvalue('<a><b>b</b><b!>b!</b!></a>','//b!');
+
+#
+# Bug #16320 XML: extractvalue() won't accept names containing underscores
+#
+select extractvalue('<A_B>A</A_B>','/A_B');

sql/item_xmlfunc.cc

@@ -1272,7 +1272,7 @@ my_xident_body(int c)
   return (((c) >= 'a' && (c) <= 'z') ||
           ((c) >= 'A' && (c) <= 'Z') ||
           ((c) >= '0' && (c) <= '9') ||
-          ((c)=='-'));
+          ((c)=='-') || ((c) == '_'));
 }