iconv: fix parameter type of utf8seq_is_{overlong,surrogate,illegal}

Use `unsigned char *s` rather than `char *s`. First, this fixes compiler
warnings when these functions are called from utf8dec_wchar() passing
the `in` pointer of type `unsigned char *`.

Second, these functions are always called with characters >= 0x80 so the
sign bit is set. Shifting right a negative signed value will insert `1`
from the left side, so `foo >> 1` where foo is negative will always have
the sign bit set. So at least "case 2" would never return true.

There is a similar problem with tests like

  (*(s+1) >= 0xA0) && (*(s+1) <= 0xBF)

This condition is always false with `char *s`.

Signed-off-by: Marcus Haehnel <marcus.haehnel@kernkonzept.com>

libiconv/iconv.c

@@ -242,7 +242,7 @@ static inline int utf8enc_wchar(char *outb, wchar_t c)
 	}
 }
 
-static inline int utf8seq_is_overlong(char *s, int n)
+static inline int utf8seq_is_overlong(unsigned char *s, int n)
 {
 	switch (n)
 	{
@@ -268,12 +268,12 @@ static inline int utf8seq_is_overlong(char *s, int n)
 	return 0;
 }
 
-static inline int utf8seq_is_surrogate(char *s, int n)
+static inline int utf8seq_is_surrogate(unsigned char *s, int n)
 {
 	return ((n == 3) && (*s == 0xED) && (*(s+1) >= 0xA0) && (*(s+1) <= 0xBF));
 }
 
-static inline int utf8seq_is_illegal(char *s, int n)
+static inline int utf8seq_is_illegal(unsigned char *s, int n)
 {
 	return ((n == 3) && (*s == 0xEF) && (*(s+1) == 0xBF) &&
 	        (*(s+2) >= 0xBE) && (*(s+2) <= 0xBF));