remove some gcc warnings

src/filter.c

@@ -337,7 +337,7 @@ static bool is_blank_line (const char *str)
  */
 int filter_fix_linedirs (struct filter *chain)
 {
-	char   buf[512];
+	char   buf[4096];
 	const size_t readsz = sizeof buf;
 	int     lineno = 1;
 	bool    in_gen = true;	/* in generated code */

src/misc.c

@@ -341,7 +341,7 @@ void lerr_fatal (const char *msg, ...)
 
 void line_directive_out (FILE *output_file, int do_infile)
 {
-	char    directive[MAXLINE], filename[MAXLINE];
+	char    directive[MAXLINE*2], filename[MAXLINE];
 	char   *s1, *s2, *s3;
 	static const char line_fmt[] = "#line %d \"%s\"\n";