YYFAIL: warn about uses and remove from lalr1.java.

* NEWS (2.5): Document.
* data/lalr1.java (parser::YYStack::YYFAIL): Rename to YYERRLAB,
and make it private.  Update all uses.
* src/scan-code.l (SC_RULE_ACTION): Implement warning.
(cherry picked from commit 4395a9ff4fd518580b9abe9482783e8eba192f34)

Conflicts:

	data/lalr1.java