Compilation warnings in auth_mapping.c

00:02:33.819 /mnt/workspace/percona-server-5.5-param/BUILD_TYPE/debug/Host/ubuntu-precise-64bit/Percona-Server/plugin/percona-pam-for-mysql/src/auth_mapping.c: In function ‘mapping_iter_next’:
00:02:33.860 /mnt/workspace/percona-server-5.5-param/BUILD_TYPE/debug/Host/ubuntu-precise-64bit/Percona-Server/plugin/percona-pam-for-mysql/src/auth_mapping.c:107:10: error: missing initializer [-Werror=missing-field-initializers]
00:02:33.860 /mnt/workspace/percona-server-5.5-param/BUILD_TYPE/debug/Host/ubuntu-precise-64bit/Percona-Server/plugin/percona-pam-for-mysql/src/auth_mapping.c:107:10: error: (near initialization for ‘token[0].token’) [-Werror=missing-field-initializers]
00:02:33.861 /mnt/workspace/percona-server-5.5-param/BUILD_TYPE/debug/Host/ubuntu-precise-64bit/Percona-Server/plugin/percona-pam-for-mysql/src/auth_mapping.c: In function ‘mapping_lookup_user’:
00:02:33.861 /mnt/workspace/percona-server-5.5-param/BUILD_TYPE/debug/Host/ubuntu-precise-64bit/Percona-Server/plugin/percona-pam-for-mysql/src/auth_mapping.c:183:30: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
00:02:33.861 cc1: all warnings being treated as errors
00:02:33.862 make[2]: *** [plugin/percona-pam-for-mysql/CMakeFiles/auth_pam.dir/src/auth_mapping.c.o] Error 1

This causes debug builds with -DWITH_PAM=ON to fail.