Make tl_yylex hookable (default is tl_lex)

This allows replacing the lexer when using libltl2ba.la.

lex.c

@@ -36,9 +36,10 @@
 
 static Symbol	*symtab[Nhash+1];
 static int	tl_lex(void);
+int (*tl_yylex)() = tl_lex;
 
 extern YYSTYPE	tl_yylval;
-char	yytext[2048];
+static char	yytext[2048];
 
 #define Token(y)        tl_yylval = tl_nn(y,ZN,ZN); return y
 
@@ -86,14 +87,6 @@ follow(int tok, int ifyes, int ifno)
 	return ifno;
 }
 
-int
-tl_yylex(void)
-{	int c = tl_lex();
-#if 0
-	printf("c = %d\n", c);
-#endif
-	return c;
-}
 
 static int
 tl_lex(void)

ltl2ba.h

@@ -260,6 +260,8 @@ extern int	tl_verbose;
 extern int	tl_terse;
 extern unsigned long	All_Mem;
 
+extern int (*tl_yylex)();               /* hook for lexer */
+
 int  ltl2ba_init();
 int  set_uform(const char *str);
 void append_uform(const char *str);

parse.c

@@ -32,7 +32,6 @@
 
 #include "ltl2ba.h"
 
-extern int	tl_yylex(void);
 extern int	tl_verbose, tl_simp_log;
 
 int	tl_yychar = 0;