improve "$arch" variable usage

- handle the (default!) undefined case;
- really treat it as a number (cause that's the way it is defined everywhere in "check_architecture", and it is compared to a number too);
- (try to) avoid extra ops by reordering the operations.
Fix for MySQL 5.6 table_open_cache

MySQL 5.6 fails silently when table_cache is used instead of table_open_cache. MySQLTuner should indicate table_open_cache instead of table_cache when printing variable suggestions.
Merge pull request #48 from ArondeParon/patch-1

Fix for MySQL 5.6 table_open_cache
Correct table_cache_var bug

Fixes #49 by correcting a small error from #48. Sorry, folks!
Fixed wget command.
Merge pull request #51 from vakuum/pr-1

Fixed wget command.
Update mysqltuner.pl

minor format fixes
Merge pull request #53 from Baebeca/master

minor format fixes
Merge pull request #45 from altblue/master

improve "$arch" variable usage
Merge pull request #1 from major/master

Update