docs: deprecate JAVA primary

docs: deprecate JAVA primary

* doc/automake.texi (Java): Deprecate the JAVA primary, stating
that it will become obsolete in automake 1.12 and probably removed
altogether in automake 1.13.  Reflect this in the section title,
by appending the string "(deprecated feature)".
(@menu, @detailmenu): Update.
(Java Support with gcj): The cross-referenced support for bytecode
compilation with the JAVA primary is rudimentary and deprecated.
State that explicitly.