Here is a list of all files with brief descriptions:

src
common
rsaref
pkcs11.h
pkcs11f.h
pkcs11t.h
alg_st.h
base64.h
cert_info.h
cert_st.h
cert_vfy.h	Several routines to:
debug.h
error.h
NSPRerrs.h
pam-pkcs11-ossl-compat.h
pkcs11_lib.h
SECerrs.h
secutil.h
SSLerrs.h
strings.h
strndup.h
uri.h	This module contains several functions to retrieve data from an URL
mappers
cn_mapper.h
digest_mapper.h
generic_mapper.h
krb_mapper.h
ldap_mapper.h
mail_mapper.h
mapper.h
mapperlist.h
ms_mapper.h
null_mapper.h
opensc_mapper.h
openssh_mapper.h
pwent_mapper.h
subject_mapper.h
uid_mapper.h
pam_pkcs11
mapper_mgr.h
pam_config.h
scconf
internal.h
scconf.h