Fixes to eliminate valgrind warnings.

sql/rpl_record.cc:
  Factoring out expression and putting it in an auto variable.
sql/rpl_utility.cc:
  Removing a check that causes compile warnings.
sql/rpl_utility.h:
  Ensuring that there is enough memory for the metadata, to avoid reads
  from uninitialized memory. Initializing the memory to keep valgrind
  quiet.

sql/rpl_record.cc

@@ -255,8 +255,9 @@ unpack_row(RELAY_LOG_INFO const *rli,
         bool save= table->s->db_low_byte_first;
         table->s->db_low_byte_first= TRUE;
 #endif
-        if (tabledef && tabledef->field_metadata(i))
-          pack_ptr= f->unpack(f->ptr, pack_ptr, tabledef->field_metadata(i));
+        uint16 const metadata= tabledef->field_metadata(i);
+        if (tabledef && metadata)
+          pack_ptr= f->unpack(f->ptr, pack_ptr, metadata);
         else
           pack_ptr= f->unpack(f->ptr, pack_ptr);
 #if 0

sql/rpl_utility.cc

@@ -97,7 +97,7 @@ uint32 table_def::calc_field_size(uint col, uchar *master_data)
   {
     uint from_len= (m_field_metadata[col] >> 8U) & 0x00ff;
     uint from_bit_len= m_field_metadata[col] & 0x00ff;
-    DBUG_ASSERT(from_bit_len >= 0 && from_bit_len <= 7);
+    DBUG_ASSERT(from_bit_len <= 7);
     length= from_len + ((from_bit_len > 0) ? 1 : 0);
     break;
   }

sql/rpl_utility.h

@@ -66,9 +66,13 @@ class table_def
   {
     m_memory= (uchar *)my_multi_malloc(MYF(MY_WME),
                                        &m_type, size,
-                              &m_field_metadata, size * sizeof(short),
-                              &m_null_bits, (m_size + 7) / 8,
+                                       &m_field_metadata,
+                                       size * sizeof(uint16),
+                                       &m_null_bits, (size + 7) / 8,
                                        NULL);
+
+    bzero(m_field_metadata, size * sizeof(uint16));
+
     if (m_type)
       memcpy(m_type, types, size);
     else