client/Makefile.am:
  Use LDADD_R as common variable for programs to be linked with thread safe library.
client/mysqlimport.c:
  Enable "--use-threads"
  Formatting
mysql-test/r/mysqldump.result:
  Update test result
mysql-test/t/disabled.def:
  Enable mysqldump
mysql-test/t/mysqldump.test:
  Enable test for mysqlimport with threads
  Add test for failed mysqlimport