Some things still fail in innodb-index.test, and there seems to be
a race condition (data dictionary lock wait) when running with --valgrind.
dfield_t: Add an "external storage" flag, dfield->ext.
dfield_is_null(), dfield_is_ext(), dfield_set_ext(), dfield_set_null():
New functions.
dfield_copy(), dfield_copy_data(): Add const qualifiers, fix in/out comments.
data_write_sql_null(): Use memset().
big_rec_field_t: Replace byte* data with const void* data.
ut_ulint_sort(): Remove.
upd_field_t: Remove extern_storage.
upd_node_t: Replace ext_vec, n_ext_vec with n_ext.
row_merge_copy_blobs(): New function.
row_ins_index_entry(): Add the parameter "ibool foreign" for suppressing
foreign key checks during fast index creation or when inserting into
secondary indexes.
btr_page_insert_fits(): Add const qualifiers.
btr_cur_add_ext(), upd_ext_vec_contains(): Remove.
dfield_print_also_hex(), dfield_print(): Replace if...else if with switch.
Observe dfield_is_ext().
accessors returning pointers with macros that preserve const qualifiers.
In UNIV_DEBUG builds, retain the accessors and cast away constness there.
dfield_get_type(), dfield_get_data(), dtuple_get_nth_field(),
dict_table_get_nth_col(), dict_table_get_sys_col(): Implement as macro
unless #ifdef UNIV_DEBUG.
rec_get_nth_field(): Replace with rec_get_nth_field_offs() that does not
do pointer arithmetics. Implement rec_get_nth_field() as a macro.
and modify some functions to return const pointers. Add const qualifiers
to local variable declarations or casts to remove the const qualifier
in those places where write access is needed.
