fix for bug with pushback of 0xFF in lexer

[Zack Weinberg]

Committed.  Fixes c-torture/execute/20000227-1.c.  See the 
"\0ÿ in strings" thread on gcc-bugs for discussion (starts at 
http://gcc.gnu.org/ml/gcc-bugs/2000-02/msg00805.html ).

zw

	* c-lex.c (putback_buffer): Make 'buffer' an unsigned char *.
===================================================================
Index: c-lex.c
--- c-lex.c	2000/02/26 05:45:17	1.75
+++ c-lex.c	2000/02/27 20:58:46
@@ -85,7 +85,7 @@ extern int yy_get_token ();
 #define UNGETC(c) put_back (c)
 
 struct putback_buffer {
-  char *buffer;
+  unsigned char *buffer;
   int   buffer_size;
   int   index;
 };