Compiling proftpd from potato in a slink box

[Paulo Henrique Baptista de Oliveira]

        I cant compile proftp from unstable in a slink server because it gives
me the following error:

gcc -Wall -g3  -I/usr/include/mysql -g -O2 -DUSESHADOW -DAUTOSHADOW
-DCONFIG_FILE_PATH=\"/etc/proftpd.conf\" -DRUN_DIR=\"/var/run/proftpd\"
-DLINUX  -I.. -I../include -c mod_pgsql.c
In file included from /usr/include/postgresql/libpq-fe.h:28,
                 from mod_pgsql.c:36:
/usr/include/postgresql/libpq/pqcomm.h:22: c.h: No such file or directory
make[2]: *** [mod_pgsql.o] Error 1
make[2]: Leaving directory `/home/baptista/PROFTPD/proftpd-1.2.0pre7/modules'
make[1]: *** [modules] Error 2
make[1]: Leaving directory `/home/baptista/PROFTPD/proftpd-1.2.0pre7'
make: *** [build] Error 2

        What is the error?
        Thanks,         Paulo Henrique