mdbx: separate and describe MDBX_DB_ACCEDE.

Change-Id: I1a846d196eb00138c1c5ec453537757b1df78d31

mdbx.h

@@ -1063,7 +1063,19 @@ enum MDBX_db_flags_t {
   MDBX_REVERSEDUP = UINT32_C(0x40),
 
   /** Create DB if not already existing */
-  MDBX_CREATE = UINT32_C(0x40000)
+  MDBX_CREATE = UINT32_C(0x40000),
+
+  /** Opens an existing sub-database created with unknown flags.
+   *
+   * The `MDBX_DB_ACCEDE` flag is intend to open a existing sub-database which
+   * was created with unknown flags (\ref MDBX_REVERSEKEY, \ref MDBX_DUPSORT,
+   * \ref MDBX_INTEGERKEY, \ref MDBX_DUPFIXED, \ref MDBX_INTEGERDUP and
+   * \ref MDBX_REVERSEDUP).
+   *
+   * In such cases, instead of returning the \ref MDBX_INCOMPATIBLE error, the
+   * sub-database will be opened with flags which it was created, and then an
+   * application could determine the actual flags by \ref mdbx_dbi_flags(). */
+  MDBX_DB_ACCEDE = MDBX_ACCEDE
 };
 #ifndef __cplusplus
 /** \ingroup c_dbi */

src/mdbx_chk.c

@@ -575,7 +575,7 @@ static int process_db(MDBX_dbi dbi_handle, char *dbi_name, visitor *handler,
 
   if (dbi_handle == ~0u) {
     rc = mdbx_dbi_open_ex(
-        txn, dbi_name, MDBX_ACCEDE, &dbi_handle,
+        txn, dbi_name, MDBX_DB_ACCEDE, &dbi_handle,
         (dbi_name && ignore_wrong_order) ? equal_or_greater : nullptr,
         (dbi_name && ignore_wrong_order) ? equal_or_greater : nullptr);
     if (rc) {