Its removal was annonced several times in NEWS (for Bison 3.5, 3.6, 3.7).
* data/skeletons/c.m4, data/skeletons/yacc.c: Remove support for YYPRINT.
* NEWS: Fix the mess introduced by the merge.
Document the removal of YYPRINT.
* doc/bison.texi (The YYPRINT Macro): Remove.