Add new cmake configuration variable -DWITH_NDBCLUSTER=[ON|OFF]
which controls building of MySQL Cluster. The difference between
MySQL Cluster and MySQL Server are:
 - custom server suffix "-cluster", indicating that the MySQL Server
   has been built for MySQL Cluster.
 - the ndbcluster plugin which makes it possible for MySQL Server
   to use the distributed NDB Cluster storage engine.
 - the NDB Cluster storage engine binaries and tools
 - the package names starts with mysql-cluster and contains the
   cluster version

In earlier versions the MySQL Server which was part of MySQL Cluster
had a modified version string including "ndb-X.Y.Z" which indicated
the version of NDB. This has now been removed and instead the custom
server suffix "-cluster" is used.

For legacy "ease of use" reasons, also allow WITH_NDBCLUSTER_STORAGE_ENGINE
and WITH_PLUGIN_NDBCLUSTER to be aliases for WITH_NDBCLUSTER unless
the latter has been specified by user. The WITHOUT_NDBCLUSTER is not
supported anymore, instead use WTTH_NDBCLUSTER=OFF. Furthermore, neither
WITH_MAX, WITH_ALL or any other options previously supported to
include the ndbcluster plugin will have any effect on whether or not
MySQL Cluster is built.

From now on MySQL Cluster uses version as defined in top level
VERSION file and same as the MySQL Server as default. It's possible
to set a specific version using the MYSQL_CLUSTER_VERSION_MAJOR,
MYSQL_CLUSTER_VERSION_MINOR, MYSQL_CLUSTER_VERSION_PATCH and
MYSQL_CLUSTER_VERSION_EXTRA in the VERSION file. However setting
these values are optional and should only be used in case the
default need to be overridden. Setting only
MYSQL_CLUSTER_VERSION_EXTRA is useful when creating a MySQL Cluster
version which is for example DMR while the contained MySQL Server is
already gone GA.

Remove the now obsolete storage/ndb/VERSION and instead
require the variable MYSQL_CLUSTER_VERSION to be defined.
Hardcode the NDB_SHARED_LIB_VERSION directly in the
CMakeLists.txt file, having it in VERSION is an automake remnant.

Remove unused MYSQL_RPM_VERSION, it's left over
from when MySQL Cluster was using a hacked rpm spec file.

Remove conditional logic which generated an unused mysql-cluster-X.Y.Z.spec
file. Everything is built from mysql.spec

Remove WITH_NDB_DEFAULT_PLUGIN_DETECT which is redundant now
when we either build MySQL Cluster or MySQL Server.

Add new variable VERSION_SRC to control the version of
the source tarball used in rpm packages.

Change mtr.pl to detect MySQL Cluster by looking
for "-cluster" in MySQL Server version string

The version string of MySQL tools now look like:
  $ mysqld --version
  mysqld  Ver 8.0.13-cluster-debug for Linux on x86_64 (Source distribution)

Where the old was:
  $ mysqld --version
  mysqld  Ver 5.7.22-ndb-7.5.5-debug for Linux on x86_64 (Source distribution)

The version string of NDB tools now look like:
  $ ndb_mgm --version
  MySQL distrib mysql-8.0.13 ndb-8.0.13-dmr-debug, for Linux (x86_64)

Where the old was:
  $ ndb_mgm --version
  MySQL distrib mysql-5.7.22 ndb-7.5.5-dmr-debug, for Linux (x86_64)

Output from version variables found in the MySQL Server:
  mysql> SELECT VERSION();
  VERSION()
  8.0.13-cluster-debug

  mysql> SELECT @@ndb_version_string;
  @@ndb_version_string
  ndb-8.0.13-dmr

Add test checking that MySQL version string contains -cluster and
that the NDB and MySQL version number matches.