Reduce compilation noise during normal compilation:
    php-5.5/ext/session/session.c:836: warning: unused variable ‘struc’
    php-5.5/ext/session/session.c:836: warning: unused variable ‘num_key’
    php-5.5/ext/session/session.c:836: warning: unused variable ‘key_length’
    php-5.5/ext/session/session.c:836: warning: unused variable ‘key’
    php-5.5/ext/session/session.c:835: warning: unused variable ‘key_type’
    php-5.5/ext/session/session.c:834: warning: unused variable ‘_ht’
    php-5.5/ext/session/session.c:857: warning: unused variable ‘has_value’
    php-5.5/ext/session/session.c:856: warning: unused variable ‘namelen’
    php-5.5/ext/session/session.c:853: warning: unused variable ‘name’
    php-5.5/ext/session/session.c:852: warning: unused variable ‘p’

    php-5.5/ext/session/mod_user.c:191: warning: unused variable ‘ret’