[AVRO-3943] Remove obsolete folders from C++ bindings (#2756)

* AVRO-3943: Remove obsolete Bison/Flex files

* AVRO-3943: Remove obsolete m4 files

* AVRO-3943: Remove mentions of bison and flex from README

lang/c++/LICENSE

@@ -201,36 +201,6 @@
    See the License for the specific language governing permissions and
    limitations under the License.
 
-----------------------------------------------------------------------
-License for the m4 macros used by the C++ implementation:
-
-Files:
-* lang/c++/m4/m4_ax_boost_system.m4
-  Copyright (c) 2008 Thomas Porschberg <[email protected]>
-  Copyright (c) 2008 Michael Tindal
-  Copyright (c) 2008 Daniel Casimiro <[email protected]>
-* lang/c++/m4/m4_ax_boost_asio.m4
-  Copyright (c) 2008 Thomas Porschberg <[email protected]>
-  Copyright (c) 2008 Pete Greenwell <[email protected]>
-* lang/c++/m4/m4_ax_boost_filesystem.m4
-  Copyright (c) 2009 Thomas Porschberg <[email protected]>
-  Copyright (c) 2009 Michael Tindal
-  Copyright (c) 2009 Roman Rybalko <[email protected]>
-* lang/c++/m4/m4_ax_boost_thread.m4
-  Copyright (c) 2009 Thomas Porschberg <[email protected]>
-  Copyright (c) 2009 Michael Tindal
-* lang/c++/m4/m4_ax_boost_regex.m4
-  Copyright (c) 2008 Thomas Porschberg <[email protected]>
-  Copyright (c) 2008 Michael Tindal
-* lang/c++/m4/m4_ax_boost_base.m4
-  Copyright (c) 2008 Thomas Porschberg <[email protected]>
-
-License text:
-| Copying and distribution of this file, with or without modification, are
-| permitted in any medium without royalty provided the copyright notice
-| and this notice are preserved. This file is offered as-is, without any
-| warranty.
-
 ----------------------------------------------------------------------
 License for the AVRO_BOOT_NO_TRAIT code in the C++ implementation:
 File: lang/c++/api/Boost.hh

lang/c++/README

@@ -39,8 +39,8 @@ mkdir build
 cd build
 cmake -G "Unix Makefiles" ..
 
-If it doesn't work, either you are missing some packages (boost, flex or bison),
-or you need to help configure locate them.
+If it doesn't work, either you are missing boost package or you need to help
+configure locate it.
 
 If the Makefile is configured correctly, then you can make and run tests: