mariadb55: fix build error on Fedora 19
mariadb55: fix build error on Fedora 19

On Fedora 19, MariaDB 5.5.31 is used as default version.
Note that Alter_info::ALTER_XXX is defined since MariaDB 10.0.4.

mroonga/mroonga,mroonga/mroonga,yoku0825/mroonga,yoku0825/mroonga,naoa/mroonga,mroonga/mroonga,yoku0825/mroonga,naoa/mroonga,naoa/mroonga,yoku0825/mroonga,naoa/mroonga,yoku0825/mroonga,yoku0825/mroonga,mroonga/mroonga,naoa/mroonga,naoa/mroonga