It's an old pam module, but still may be in use... During compilation of
3.0.20rc1 bunch of warning spitted:

Compiling pam_smbpass/pam_smb_auth.c with -fPIC -DPIC
In file included from pam_smbpass/pam_smb_auth.c:33:
pam_smbpass/general.h:54:1: warning: "strncasecmp" redefined
In file included from include/includes.h:994,
                 from pam_smbpass/pam_smb_auth.c:21:
include/safe_string.h:62:1: warning: this is the location of the previous definition
pam_smbpass/pam_smb_auth.c: In function `pam_sm_setcred':
pam_smbpass/pam_smb_auth.c:165: warning: passing arg 3 of `pam_get_data' from
incompatible pointer type
Compiling pam_smbpass/pam_smb_passwd.c with -fPIC -DPIC
In file included from pam_smbpass/pam_smb_passwd.c:37:
pam_smbpass/general.h:54:1: warning: "strncasecmp" redefined
In file included from include/includes.h:994,
                 from pam_smbpass/pam_smb_passwd.c:25:
include/safe_string.h:62:1: warning: this is the location of the previous definition
pam_smbpass/pam_smb_passwd.c: In function `pam_sm_chauthtok':
pam_smbpass/pam_smb_passwd.c:227: warning: passing arg 3 of `pam_get_data' from
incompatible pointer type
Compiling pam_smbpass/pam_smb_acct.c with -fPIC -DPIC
In file included from pam_smbpass/pam_smb_acct.c:32:
pam_smbpass/general.h:54:1: warning: "strncasecmp" redefined
In file included from include/includes.h:994,
                 from pam_smbpass/pam_smb_acct.c:21:
include/safe_string.h:62:1: warning: this is the location of the previous definition
Compiling pam_smbpass/support.c with -fPIC -DPIC
In file included from pam_smbpass/support.c:19:
pam_smbpass/general.h:54:1: warning: "strncasecmp" redefined
In file included from include/includes.h:994,
                 from pam_smbpass/support.c:18:
include/safe_string.h:62:1: warning: this is the location of the previous definition
pam_smbpass/support.c: In function `make_remark':
pam_smbpass/support.c:117: warning: assignment discards qualifiers from pointer
target type
pam_smbpass/support.c: In function `_smb_verify_password':
pam_smbpass/support.c:387: warning: passing arg 3 of `pam_get_data' from
incompatible pointer type
pam_smbpass/support.c: In function `_smb_read_password':
pam_smbpass/support.c:518: warning: assignment discards qualifiers from pointer
target type
pam_smbpass/support.c:526: warning: assignment discards qualifiers from pointer
target type
pam_smbpass/support.c:531: warning: assignment discards qualifiers from pointer
target type
pam_smbpass/support.c:597: warning: passing arg 3 of `pam_get_data' from
incompatible pointer type

Nothing fatal, but still... Here is the patch, that seems fixes the problems.