Handle unsigned integer types as their signed versions.

Map "unsigned short/int/long" to "short/int/long" instead of "unsigned long
long" they were all mapped to before. Unsigned variants can be compared to the
signed ones and back without loss but "unsigned long long" has a different
size and so can't always be converted from.

Signed-off-by: Vadim Zeitlin <vz-soci@zeitlins.org>

src/backends/mysql/statement.cpp

@@ -378,7 +378,8 @@ void mysql_statement_backend::describe_column(int colNum,
     case FIELD_TYPE_SHORT:      //MYSQL_TYPE_SHORT:
     case FIELD_TYPE_INT24:      //MYSQL_TYPE_INT24:
     case FIELD_TYPE_LONG:       //MYSQL_TYPE_LONG:
-        type = dt_integer;
+        type = field->flags & UNSIGNED_FLAG ? dt_long_long
+                                            : dt_integer;
         break;
     case FIELD_TYPE_LONGLONG:   //MYSQL_TYPE_LONGLONG:
         type = field->flags & UNSIGNED_FLAG ? dt_unsigned_long_long :

src/core/exchange-traits.h

@@ -48,13 +48,23 @@ struct exchange_traits<short>
     enum { x_type = x_short };
 };
 
+template <>
+struct exchange_traits<unsigned short> : exchange_traits<short>
+{
+};
+
 template <>
 struct exchange_traits<int>
 {
     typedef basic_type_tag type_family;
     enum { x_type = x_integer };
 };
 
+template <>
+struct exchange_traits<unsigned int> : exchange_traits<int>
+{
+};
+
 template <>
 struct exchange_traits<char>
 {
@@ -88,6 +98,11 @@ struct exchange_traits<long int>
     enum { x_type = long_traits_helper<sizeof(long int)>::x_type };
 };
 
+template <>
+struct exchange_traits<unsigned long> : exchange_traits<long>
+{
+};
+
 template <>
 struct exchange_traits<double>
 {