Adjust lex processing in generic for newer lex (flex & Co.).

The hack to replace the getc() in the input does not work anymore due
to structural changes in the generated code (buffering in lex.yy.c).

This needs to implement lex specific tell() and seek() functions. See
https://stackoverflow.com/questions/44266589 for a detailed discussion
of the problem.

unix/boot/generic/generic.c

@@ -18,7 +18,7 @@
 
 #define	input		lex_input
 #define	unput		lex_unput
-extern	char yytext[];
+extern	char *yytext;
 extern	int  yyleng;
 extern	FILE *yyin;
 extern	FILE *yyout;
@@ -45,14 +45,11 @@ char	type_char;
 int	pass_output = 1;
 int	clobber = NO;
 
-extern long  k_ftell (FILE *cx_i);
-extern FILE *k_fopen (char *fname, char *mode);
-extern int   k_fseek (FILE *cx_i, long offset, int type);
-extern int   k_fclose (FILE *cx_i);
-
 extern int   yylex (void);
 extern int   lex_input (void);
 extern void  lex_unput (int ch);
+extern long lex_tell (void);
+extern void lex_seek (long fpos);
 
 
 char *make_typed_filename (char *template, char type_char);
@@ -136,7 +133,7 @@ int main (int argc, char *argv[])
 
 	for (n=0;  n < nfiles;  n++) {
 	    strcpy (input_file, files[n]);
-	    yyin = k_fopen (input_file, "r");
+	    yyin = fopen (input_file, "r");
 	    if (yyin == NULL) {
 		fprintf (stderr, "Cannot open input file '%s'\n", input_file);
 		continue;
@@ -218,10 +215,10 @@ int main (int argc, char *argv[])
 		yylex();	/* do it */
 
 		fclose (fp);
-		k_fseek (yyin,0L,0);
+		lex_seek (0L);
 	    }
 
-	    k_fclose (yyin);
+	    fclose (yyin);
 	}
 
 	exit (OSOK);
@@ -525,7 +522,7 @@ do_for (void)
 	fp->f_prevtype = type_char;
 	strcpy (fp->f_types, types);
 	fp->f_curtype = fp->f_types;
-	fp->f_fpos = k_ftell (yyin);
+	fp->f_fpos = lex_tell();
 
 	type_char = *(fp->f_curtype)++;
 	set_type_string (type_char);
@@ -549,7 +546,7 @@ do_endfor (void)
 	fp = &forstk[forlev];
 	if ((type_char = *(fp->f_curtype)++) != EOS) {
 	    set_type_string (type_char);
-	    k_fseek (yyin, fp->f_fpos, 0);
+	    lex_seek (fp->f_fpos);
 	} else {
 	    type_char = fp->f_prevtype;
 	    set_type_string (type_char);