Changed mysql-test-run.sh to test for files to get shorter, more reliable timeouts.


Docs/manual.texi:
  Cleaned up SET PASSWORD stuff
client/mysqltest.c:
  Do more retrys
mysql-test/mysql-test-run.sh:
  Test for files to get shorter timeouts
mysql-test/r/query_cache.result:
  Portability fix
mysql-test/t/query_cache.test:
  Portability fix
sql/sql_cache.cc:
  Safety fix