[Dovecot] Antispam plugin, compile under osx

[Johannes Berg]

> cc  -fPIC -shared -Wall -Wextra -DPLUGINNAME=antispam -DHAVE_CONFIG_H - 
> I/opt/local/include/dovecot/ -I/opt/local/include/dovecot/src/ -I/opt/ 
> local/include/dovecot/src/lib/ -I/opt/local/include/dovecot/src/lib- 
> storage/ -I/opt/local/include/dovecot/src/lib-mail/ -I/opt/local/ 
> include/dovecot/src/lib-imap/ -I/opt/local/include/dovecot/src/lib- 
> dict/ -I/opt/local/include/dovecot/src/lib-index/ -I/opt/local/include/ 
> dovecot/src/imap/ signature.o antispam-plugin.o antispam-storage.o  
> dspam-exec.o -o lib90_antispam_plugin.so
> Undefined symbols:
>    "_mailbox_get_name", referenced from:
>        _mailbox_patternmatch in antispam-plugin.o
>        _mailbox_is_spam in antispam-plugin.o
>        _mailbox_is_trash in antispam-plugin.o
>        _mailbox_is_unsure in antispam-plugin.o

Looks like your linker is prepending _ to each symbol, which probably
don't exist since dovecot itself exports w/o the underscore ... I have
no idea why it's doing that though.

johannes