Use only unsigned values in the implementatin of LIKE and GLOB so that

values won't overflow to negative when dealing with malformed UTF8.

FossilOrigin-Name: 77f01578bb565d1bc884b374b68bae10ce34a084

src/utf.c

@@ -163,7 +163,7 @@ static const unsigned char sqlite3Utf8Trans1[] = {
         || (c&0xFFFFF800)==0xD800                          \
         || (c&0xFFFFFFFE)==0xFFFE ){  c = 0xFFFD; }        \
   }
-int sqlite3Utf8Read(
+u32 sqlite3Utf8Read(
   const unsigned char *zIn,       /* First byte of UTF-8 character */
   const unsigned char **pzNext    /* Write first byte past UTF-8 char here */
 ){