Fix problem with strange printout of line numbers, detected on aix52, but existing on all platforms, just being masked by init of vars to zero.


client/mysqltest.c:
  Remove lineno_stack, instead use the already existing file_stack and add a new variable lineno to keep track of what line in the file we are at.
mysql-test/r/mysqltest.result:
  Correct test result, "At line 1" should be printed