mail-log: Removed unnecessary code.

Use -Wl,--as-needed -Wl,--no-undefined GNU ld flags for non-plugins.

Added dovecot.m4 file that external plugins can use. Based on patch by Dennis Schridde. --HG-- branch : HEAD

OSX: Don't try add plugin dependencies. It just breaks plugin loading. --HG-- branch : HEAD

plugins: Added dependencies. The dependencies can only be checked if the dlopen() can successfully open the module, so use (apparently) non-portable ltlibrary linking to force the libraries we depend on to load with us. --HG-- branch : HEAD

Reimplemented mail-log plugin using notify plugin framework. Patch by Mark Washenberger / Rackspace. --HG-- branch : HEAD

Get rid of imap/, pop3/, lda/ and sql/ module subdirs. It's all in lib/dovecot/ now. --HG-- branch : HEAD

mail-log plugin: Added flag_change event and flags field. --HG-- branch : HEAD

Previous changes broke plugin symlink creation in make install. --HG-- branch : HEAD

Use dynamic module suffix provided by libtool rather than hardcoded ".so". --HG-- branch : HEAD

Added mail_log plugin to log various mail operations. Currently it logs mail copies, deletions, expunges and mailbox deletions. --HG-- branch : HEAD