Problem: even if an Item_xml_str_func successor returns NULL, it doesn't have
a corresponding property (maybe_null) set, that leads to a failed assertion.
Fix: set nullability property of Item_xml_str_func.
Changed test for functions if they are supported.
3 categories:
1) Fully supported
2) Supported for single character collations
3) Supported for binary collations
libmysqld/Makefile.am:
sql/Makefile.am:
Adding new source files.
Adding new file into build process.
include/my_xml.h:
strings/xml.c:
Adding new XML parse flags to skip text normalization and
to use relative tag names. Adding enum for XML token types.
sql/lex.h:
Making parser aware of new SQL functions.
sqll/item_create.h, sql/item_create.cc:
Adding creators for ExtractValue and UpdateXML.
sql/item.h:
Adding new Item types: nodeset and nodeset comparator.
sql/item_xmlfunc.h
sql/item_xmlfunc.cc
Adding new classes implementing XPath functions.
mysql-test/t/xml.test, mysql-test/r/xml.result:
New files: adding test case