and add a magic property to disable it again

People using the JRE won't have it and it has been removed from
OpenJDK with Java 9, it seems.

https://bz.apache.org/bugzilla/show_bug.cgi?id=40455

Suggested by Vladimir Sitnikov

Property enumerator

fixes https://bz.apache.org/bugzilla/show_bug.cgi?id=50179

test by Sai Kiran

Class.newInstance() is deprecated in Java 9+

Remove duplicated code

Another getCheckedRef() refactoring

Extract LegacyPlainResultFormatter.Stats#appendElapsed

Superfluous escapes

Correct javadoc

Task AntStructure renders a project DTD. In AntStructure class DTDPrinter, line 327, a single statement is used to concatenate a list of enumerated values which are valid for an attribute. The list is enclosed in parentheses. At line 348 the string "#IMPLIED" is appended to all attribute definitions regardless of type. For other types like Boolean and CDATA, a space is appended. Not for these enumerations. This results in a DTD validation error. Ref [XERCES definition](https://xerces.apache.org/xerces-j/apiDocs/org/apache/xerces/utils/XMLMessages.html#MSG_SPACE_REQUIRED_BEFORE_DEFAULTDECL_IN_ATTDEF)

The full message displayed in VSCode may be different from elsewhere:

    White space is required before the attribute default in the declaration
    of attribute "x" for element "y".
    xml(MSG_SPACE_REQUIRED_BEFORE_DEFAULTDECL_IN_ATTDEF)

This simple one-line change appends the space character required to avoid that error.

**Note:** This should not be modified into a change on the `joinAlts` Collector which surrounds values in parentheses. That Collector is used elsewhere where regex syntax is applied immediately after. See line 298. That asterisk cannot be separated from the values with a space. The space must only be applied to line 327.

This closes #106 pull request at github/apache/ant repo

This closes #105 pull request at github/apache/ant repo