skeletons: no longer call yylex via a CPP macro

skeletons: no longer call yylex via a CPP macro

The YYLEX existed only to support YYLEX_PARAM, which is now removed.
This macro was a nuisance, since incorrect yylex calls where pointed
the macro _use_, instead of its definition.

* data/c.m4 (b4_lex_formals, b4_lex): New.
* data/glr.c, data/yacc.c: Use it.
* data/lalr1.cc (b4_lex): New.
Use it.

squash! skeletons: no longer call yylex via a CPP macro