its: Add ability to check *.its and *.loc files with XML Schema 1.1.

its: Add ability to check *.its and *.loc files with XML Schema 1.1.

* gettext-tools/src/its.xsd10: Renamed from gettext-tools/src/its.xsd.
(RulesType): Enumerate all possible rules in the ITS namespace, instead of using
a wildcard.
(OtherRuleType): New element.
* gettext-tools/src/its.xsd11: Copied from gettext-tools/src/its.xsd.
(LocNoteRuleType): Enable assertion.
* gettext-tools/src/locating-rules.xsd10: Renamed from
gettext-tools/src/locating-rules.xsd.
* gettext-tools/src/locating-rules.xsd11: Copied from
gettext-tools/src/locating-rules.xsd.
(LocatingRuleType): Enable assertion.
* gettext-tools/src/Makefile.am (schema_DATA): Add its.xsd10, its.xsd11,
locating-rules.xsd10, locating-rules.xsd11. Remove its.xsd, locating-rules.xsd.
* gettext-tools/build-aux/xml-validate-10.in: New file.
* gettext-tools/build-aux/xml-validate-11.in: New file.
* gettext-tools/configure.ac: Substitute HAVE_JAVAEXEC.
(AC_CONFIG_FILES): Create build-aux/xml-validate-10, build-aux/xml-validate-11.
* gettext-tools/Makefile.am (DISTCLEANFILES): Add build-aux/xml-validate-10,
build-aux/xml-validate-11.
* gettext-tools/its/Makefile.am: Revert last commit.
(check-local): Check each file both using the XML Schema 1.0 and the XML Schema
1.1.
* gettext-tools/doc/gettext.texi (ITS Rules): Mention the two versions of
its.xsd.
(Location Rules): Mention the two versions of locating-rules.xsd.
* HACKING: Mention Xerces2-J.