- Evaluate all variables in the text before printing it to result file


client/mysqltest.c:
  Update echo command to vvaluate all variables in the string before printing, allow
  for variable names to be escaped using \
mysql-test/r/mysqltest.result:
  Update results for echo
mysql-test/t/mysqltest.test:
  Add more advanced tests for echo of strings with several variables 
  and/or text plus variables. Also test that variables can be escaped