rpl: repack table_def

1. Change m_size to uint. This removes some implicit conversions.
  See unpack_row, for instance:
  uint max_cols= MY_MIN(tabledef->size(), cols->n_bits);
2. Improve table_def memory layout by reordering columns

sql/rpl_utility.cc

@@ -176,8 +176,8 @@ PSI_memory_key key_memory_table_def_memory;
 table_def::table_def(unsigned char *types, ulong size,
                      uchar *field_metadata, int metadata_size,
                      uchar *null_bitmap, uint16 flags)
-  : m_size(size), m_type(0), m_field_metadata_size(metadata_size),
-    m_field_metadata(0), m_null_bits(0), m_flags(flags),
+  : m_type(0), m_size(size), m_field_metadata_size(metadata_size),
+    m_field_metadata(0), m_flags(flags), m_null_bits(0),
     m_memory(NULL)
 {
   m_memory= (uchar *)my_multi_malloc(key_memory_table_def_memory, MYF(MY_WME),

sql/rpl_utility.h

@@ -63,7 +63,7 @@ class table_def
 
     @return The number of fields that there is type data for.
    */
-  ulong size() const { return m_size; }
+  uint size() const { return m_size; }
 
 
   /**
@@ -221,12 +221,12 @@ class table_def
 
 
 private:
-  ulong m_size;           // Number of elements in the types array
   unsigned char *m_type;  // Array of type descriptors
+  uint m_size;           // Number of elements in the types array
   uint m_field_metadata_size;
   uint16 *m_field_metadata;
-  uchar *m_null_bits;
   uint16 m_flags;         // Table flags
+  uchar *m_null_bits;
   uchar *m_memory;
 };