charset.c: fix -Wpointer-sign

$ make WERROR_CFLAGS="-Wpointer-sign -Werror" charset.o 2>&1 1>/dev/null
../../src/gdb/charset.c: In function ‘wchar_iterate’:
../../src/gdb/charset.c:665:13: error: pointer targets in assignment differ in signedness [-Werror=pointer-sign]
../../src/gdb/charset.c:691:13: error: pointer targets in assignment differ in signedness [-Werror=pointer-sign]
../../src/gdb/charset.c:706:12: error: pointer targets in assignment differ in signedness [-Werror=pointer-sign]

The encoding conversion code works with gdb_byte arrays as the generic
buffers that hold strings of any encoding/width.  Changing the type of
this field to gdb_byte* removes the need for one cast, and makes
everything work with the same types.  That's good -- WRT to strings,
"char *" is (almost) consistently throughout GDB only used for
ascii-ish strings.

gdb/
2013-03-07  Pedro Alves  <palves@redhat.com>

	* charset.c (struct wchar_iterator) <input>: Change type to 'const
	gdb_byte *'.
	(make_wchar_iterator): Remove cast to char*.
	(wchar_iterate): Change type of local.

2 files changed, 10 insertions, 3 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index ceeecb7..a57e2c1 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,12 @@
 2013-03-07  Pedro Alves  <palves@redhat.com>
 
+	* charset.c (struct wchar_iterator) <input>: Change type to 'const
+	gdb_byte *'.
+	(make_wchar_iterator): Remove cast to char*.
+	(wchar_iterate): Change type of local.
+
+2013-03-07  Pedro Alves  <palves@redhat.com>
+
 	* regcache.c (regcache_xmalloc_1): Call XCALLOC with signed char
 	for 'regcache->register_status'.
 
diff --git a/gdb/charset.c b/gdb/charset.c
index 165f90f..4cd6f20 100644
--- a/gdb/charset.c
+++ b/gdb/charset.c
@@ -571,7 +571,7 @@ struct wchar_iterator
   iconv_t desc;
 
   /* The input string.  This is updated as convert characters.  */
-  char *input;
+  const gdb_byte *input;
   /* The number of bytes remaining in the input.  */
   size_t bytes;
 
@@ -597,7 +597,7 @@ make_wchar_iterator (const gdb_byte *input, size_t bytes,
 
   result = XNEW (struct wchar_iterator);
   result->desc = desc;
-  result->input = (char *) input;
+  result->input = input;
   result->bytes = bytes;
   result->width = width;
 
@@ -641,7 +641,7 @@ wchar_iterate (struct wchar_iterator *iter,
   while (iter->bytes > 0)
     {
       char *outptr = (char *) &iter->out[0];
-      char *orig_inptr = iter->input;
+      const gdb_byte *orig_inptr = iter->input;
       size_t orig_in = iter->bytes;
       size_t out_avail = out_request * sizeof (gdb_wchar_t);
       size_t num;