MDEV-274: Fix unresolved link-time references

Field::marked_for_read() and Field::marked_for_write_or_computed()
are being called from plugin/type_inet/sql_type_inet.cc ever since
commit 6ea5c2b5
and thus they cannot be declared inline any more.

sql/field.cc

@@ -58,7 +58,7 @@ const char field_separator=',';
                         ((ulong) ((1LL << MY_MIN(arg, 4) * 8) - 1))
 
 // Column marked for read or the field set to read out or record[0] or [1]
-inline bool Field::marked_for_read() const
+bool Field::marked_for_read() const
 {
   return !table ||
          (!table->read_set ||
@@ -73,7 +73,7 @@ inline bool Field::marked_for_read() const
   changed fields with DBUG_FIX_WRITE_SET() in table.cc
 */
 
-inline bool Field::marked_for_write_or_computed() const
+bool Field::marked_for_write_or_computed() const
 {
   return (!table ||
           (!table->write_set ||