ITS#1732 signed/unsigned fixes

libraries/liblber/encode.c

libraries/liblber/io.c

libraries/libldap/cache.c

libraries/libldap/request.c

libraries/libldap/result.c

libraries/libldap/schema.c

libraries/libldap/utf-8-conv.c

libraries/liblunicode/ure/ure.c

libraries/liblutil/passwd.c