mdbx: release v0.9.1

Added features:

 - Preliminary C++ API with support for C++17 polymorphic allocators.
 - [Online C++ API reference](https://erthink.github.io/libmdbx/) by Doxygen.
 - Quick reference for Insert/Update/Delete operations.
 - Explicit `MDBX_SYNC_DURABLE` to sync modes for API clarity.
 - Explicit `MDBX_ALLDUPS` and `MDBX_UPSERT` for API clarity.
 - Support for read transactions preparation (`MDBX_TXN_RDONLY_PREPARE` flag).
 - Support for cursor preparation/(pre)allocation and reusing (`mdbx_cursor_create()` and `mdbx_cursor_bind()` functions).
 - Support for checking database using specified meta-page (see `mdbx_chk -h`).
 - Support for turn to the specific meta-page after checking (see `mdbx_chk -h`).
 - Support for explicit reader threads (de)registration.
 - The `mdbx_txn_break()` function to explicitly mark a transaction as broken.
 - Improved handling of corrupted databases by `mdbx_chk` utility and `mdbx_walk_tree()` function.
 - Improved DB corruption detection by checking parent-page-txnid.
 - Improved opening large DB (> 4Gb) from 32-bit code.
 - Provided `pure-function` and `const-function` attributes to C API.
 - Support for user-settable context for transactions & cursors.
 - Revised API and documentation related to Handle-Slow-Readers callback feature.

Deprecated functions and flags:

 - For clarity and API simplification the `MDBX_MAPASYNC` flag is deprecated.
   Just use `MDBX_SAFE_NOSYNC` or `MDBX_UTTERLY_NOSYNC` instead of it.
 - `MDBX_oom_func`, `mdbx_env_set_oomfunc()` and `mdbx_env_get_oomfunc()`
   replaced with `MDBX_hsr_func`, `mdbx_env_get_hsr` and `mdbx_env_get_hsr()`.

Fixes:

 - Fix `mdbx_strerror()` for `MDBX_BUSY` error (no error description is returned).
 - Fix update internal meta-geo information in read-only mode (`EACCESS` or `EBADFD` error).
 - Fix `mdbx_page_get()` null-defer when DB corrupted (crash by `SIGSEGV`).
 - Fix `mdbx_env_open()` for re-opening after non-fatal errors (`mdbx_chk` unexpected failures).
 - Workaround for MSVC 19.27 `static_assert()` bug.
 - Doxygen descriptions and refinement.
 - Update Valgrind's suppressions.
 - Workaround to avoid infinite loop of 'nested' testcase on MIPS under QEMU.
 - Fix a lot of typos & spelling (Thanks to Josh Soref for PR).
 - Fix `getopt()` messages for Windows (Thanks to Andrey Sporaw for reporting).
 - Fix MSVC compiler version requirements (Thanks to Andrey Sporaw for reporting).
 - Workarounds for QEMU's bugs to run tests for cross-builded library under QEMU.
 - Now C++ compiler optional for building by CMake.

TODO for next version(s):

 - Rework/speedup the implementation of the dirty page list (lazy compactification, lazy sorting via merge).
 - Finalize C++ API (few typos and trivia bugs are likely for now).
 - Packages for ROSA Linux, ALT Linux, Fedora/RHEL, Debian/Ubuntu.

Change-Id: I668d77e4545d444b60708b8c64a66ce43b2c56a0

ChangeLog.md

@@ -10,7 +10,7 @@ TODO:
  - Packages for ROSA Linux, ALT Linux, Fedora/RHEL, Debian/Ubuntu.
 
 
-## v0.9.1 2020-09-30 (scheduled)
+## v0.9.1 2020-09-30
 
 Added features:
 

appveyor.yml

@@ -1,4 +1,4 @@
-version: 0.9.0.{build}
+version: 0.9.1.{build}
 
 environment:
   matrix:

mdbx.h

@@ -478,7 +478,7 @@ typedef mode_t mdbx_mode_t;
 extern "C" {
 #endif
 
-/* MDBX version 0.9.x (development) */
+/* MDBX version 0.9.x */
 #define MDBX_VERSION_MAJOR 0
 #define MDBX_VERSION_MINOR 9