[Dovecot] Pigeonhole Sieve Extprograms dovecot path?

[voytek at sbt.net.au]

trying to install Pigeonhole Sieve Extprograms
how do I determine what is correct path for dovecot.config ?

I did the
hg clone http://hg.rename-it.nl/pigeonhole-0.3-sieve-extprograms/
'./autogen.sh' seemed to have worked, but './configure' fails with

# ./configure --with-dovecot=/usr/local/lib/dovecot
...
checking whether to build static libraries... yes
checking for dovecot-config in "/usr/local/lib/dovecot"... not found
configure:
configure: Use --with-dovecot=DIR to provide the path to the
dovecot-config file.
configure: error: dovecot-config not found

or

...
checking for dovecot-config in "/usr/lib64/dovecot"... not found
configure:
configure: Use --with-dovecot=DIR to provide the path to the
dovecot-config file.
configure: error: dovecot-config not found


# whereis dovecot
dovecot: /usr/sbin/dovecot /etc/dovecot /usr/lib64/dovecot
/usr/libexec/dovecot /usr/share/man/man1/dovecot.1.gz
# dovecot --version
2.1.17
# uname -a
Linux 2.6.32-431.5.1.el6.x86_64 #1 SMP Wed Feb 12 00:41:43 UTC 2014 x86_64
x86_64 x86_64 GNU/Linux