Fix for bug #32221: bug25714, mytest, mysql_client_test complaints and

crashes.

MySQL distributions contain a number of programs that are used only by
the MySQL test suite internally, i.e. they are not indended to be
invoked directly by a user. As a result, such programs are not
documented, do not have any built-in help or proper error reporting,
which may confuse users.

This patch fixes the problem with the following changes:
- mytest, libmysqltest and all references to them were removed from the
distribution since they are not used anymore
- bug25714 now displays an error message when run with incorrect
arguments or with the --help option
- mysql_client_test now does not call abort() in case of errors,
instead it does a clean exit() with a proper error status.

tests/mysql_client_test.c

@@ -123,7 +123,7 @@ static void die(const char *file, int line, const char *expr)
   fflush(stdout);
   fprintf(stderr, "%s:%d: check failed: '%s'\n", file, line, expr);
   fflush(stderr);
-  abort();
+  exit(1);
 }