Fix some warnings on Windows compilation

- silence warnings in ed25519 reference implementation
- fix signed/unsigned warning in popular header item_func.h

plugin/auth_ed25519/CMakeLists.txt

@@ -14,8 +14,12 @@ SET(REF10_SOURCES
 INCLUDE_DIRECTORIES(${CMAKE_CURRENT_SOURCE_DIR})
 
 ADD_CONVENIENCE_LIBRARY(ref10 ${REF10_SOURCES})
+IF(MSVC)
+   # Silence conversion (integer truncantion) warnings from reference code
+  SET_TARGET_PROPERTIES(ref10 PROPERTIES COMPILE_FLAGS "/wd4244 /wd4146")
+ENDIF()
 
-MYSQL_ADD_PLUGIN(auth_ed25519 server_ed25519.c ${REF10_SOURCES} MODULE_ONLY)
+MYSQL_ADD_PLUGIN(auth_ed25519 server_ed25519.c MODULE_ONLY LINK_LIBRARIES ref10)
 
 MYSQL_ADD_PLUGIN(client_ed25519 client_ed25519.c MODULE_ONLY
   CLIENT LINK_LIBRARIES mysys_ssl ref10 COMPONENT ClientPlugins)

sql/item_func.h

@@ -633,7 +633,7 @@ public:
       Reserve max_length to fit at least one character for one digit,
       plus one character for the sign (if signed).
     */
-    set_if_bigger(char_length, 1 + (unsigned_flag ? 0 : 1));
+    set_if_bigger(char_length, 1U + (unsigned_flag ? 0 : 1));
     fix_char_length(char_length);
   }
   virtual void print(String *str, enum_query_type query_type);

sql/sql_lex.cc

@@ -469,7 +469,7 @@ int my_wc_mb_utf8_with_escape(CHARSET_INFO *cs, my_wc_t escape, my_wc_t wc,
   DBUG_ASSERT(escape > 0);
   if (str + 1 >= end)
     return MY_CS_TOOSMALL2;  // Not enough space, need at least two bytes.
-  *str= escape;
+  *str= (uchar)escape;
   int cnvres= my_charset_utf8_handler.wc_mb(cs, wc, str + 1, end);
   if (cnvres > 0)
     return cnvres + 1;       // The character was normally put