Issue #1 Add support for MySQL

When compile the source code, you should type the command like
following:
make -f makefile.mysql

The "mysql-queries-template" directory redefine the TPC-H queries's
template for MySQL.

The "mysqlqgen" will generate TPC-H queries in the "mysql-queries"
directory according to the template.

The "mysqlqgen_explain" will generate TPC-H queries's execution plan
in the "mysql-queries-explain" directory according to the template.