The error was: 
"Error opening plugin module; module='afsql', error='/usr/local/syslog-ng-test/lib/syslog-ng/libafsql.so: undefined symbol: dbi_result_free'

#ldd /usr/local/syslog-ng-test/lib/syslog-ng/libafsql.so 

        linux-gate.so.1 =>  (0xb7749000)
libsyslog-ng-3.3.1.so => /usr/local/syslog-ng-test/lib/libsyslog-ng-3.3.1.so (0xb76d1000)
libssl.so.0.9.8 => /usr/lib/i686/cmov/libssl.so.0.9.8 (0xb7686000)
libcrypto.so.0.9.8 => /usr/lib/i686/cmov/libcrypto.so.0.9.8 (0xb7532000)
libpthread.so.0 => /lib/i686/cmov/libpthread.so.0 (0xb7519000)
libc.so.6 => /lib/i686/cmov/libc.so.6 (0xb73be000)
/lib/ld-linux.so.2 (0xb774a000)
libdl.so.2 => /lib/i686/cmov/libdl.so.2 (0xb73ba000)
libz.so.1 => /usr/lib/libz.so.1 (0xb73a5000)

I installed libdbi-0.8.4 and libdbi-drivers-0.8.3-1
Syslog-ng version 3.3.1

#        ./configure --prefix=/usr/local/syslog-ng-test \
> EVTLOG_CFLAGS="-I/usr/local/eventlog/include/eventlog" \
> EVTLOG_LIBS="-L/usr/local/eventlog/lib -levtlog" \
> GLIB_CFLAGS="-I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include" \
> GLIB_LIBS="-L/usr/lib -lglib-2.0 -lintl" \
> LIBDBI_CFLAGS="-I/usr/include/dbi" \
> LIBDBI_LIBS="-L/usr/lib" \
> --enable-sql \
> --enable-mixed-linking
#        make && make install