myisam_mmap_size value?

http://dev.mysql.com/worklog/task/?id=5302

We will declare 'myisam_use_mmap' obsolete, still having it around for some time. When 'myisam_use_mmap' is ON 'myisam_mmap_size' gets maximum value, when OFF 'myisam_mmap_size' is 0.

'myisam_mmap_size' minimum allowed and default values should be changed to 0. Will affect both compressed and uncompressed tables (currently only compressed tables are affected).

New status variable 'myisam_mmap_used' should be added reflecting amount of address space used for mmap.