Bug#29125 Windows Server X64: so many compiler warnings

- Remove bothersome warning messages.  This change focuses on the warnings 
that are covered by the ignore file: support-files/compiler_warnings.supp.
- Strings are guaranteed to be max uint in length

sql/sql_lex.h

@@ -1361,7 +1361,7 @@ public:
   /** Get the utf8-body length. */
   uint get_body_utf8_length()
   {
-    return m_body_utf8_ptr - m_body_utf8;
+    return (uint) (m_body_utf8_ptr - m_body_utf8);
   }
 
   void body_utf8_start(THD *thd, const char *begin_ptr);