log: Add "disable log prefix" flag to log lines

lib: Add failure_context.log_prefix to override the default

lib: Add i_log_typev()

lib: Added i_get_failure_prefix()

log_timestamp setting supports now %{usecs} This is mainly useful for debugging.

i_set_failure_prefix() now takes printf-like parameters. This avoids using t_strdup_printf() with it, which was done very commonly.

liblib: Added failure_log_type_names[] array.

Added i_set_failure_send_prefix() and renamed i_set_failure_ip() to _send_ip().

Failure logging supports now getting timestamp as parameter.

Cleaned up log callbacks and made them more extensible. fatal_failure_callback_t type is now gone, there's only failure_callback_t left that has a struct pointer as parameter. More parameters can be easily added to the struct in future.

Added debug_log_path setting and i_debug() call. Patch by Pascal Volk. --HG-- branch : HEAD

Added ATTR_HOT and ATTR_COLD macros. Use them in a couple of places. --HG-- branch : HEAD

Added i_get_failure_handlers(). --HG-- branch : HEAD

Removed LOG_TYPE_ERROR_IGNORE_IF_SEEN_FATAL. It's no longer necessary. --HG-- branch : HEAD

Initial commit for v2.0 master rewrite. Several features are still missing. --HG-- branch : HEAD

pop3/imap: When master closes our log fd, don't die when trying to log disconnect reason. --HG-- branch : HEAD

If login process crashes, log the IP address that (maybe) caused it. --HG-- branch : HEAD

Logging: Support specifying a prefix also for syslog logging. --HG-- branch : HEAD

Default failure functions are now public. --HG-- branch : HEAD

Make failure_log_type_prefixes[] and failure_exit() public. --HG-- branch : HEAD

Fix for compiling with g++ 3.x. --HG-- branch : HEAD

Changed failure callbacks to take failure type parameter, so it's no longer necessary to have separate panic and warning callbacks. Added i_log_type() function to log a message with any type (even fatal/panic without dying ourself). --HG-- branch : HEAD

Renamed __attr_*__ to ATTR_*. Renamed __attrs_used__ to ATTRS_DEFINED. --HG-- branch : HEAD

Changed .h ifdef/defines to use <NAME>_H format. --HG-- branch : HEAD

Added i_set_failure_prefix() --HG-- branch : HEAD

Added i_set_failure_exit_callback() --HG-- branch : HEAD

Added sentinel GCC attribute to *_strconcat() functions. Added format printf-attribute to vprintf-type functions. --HG-- branch : HEAD

Write all logging through master process. Fixes problems with log rotation, chrooting, etc. Master process also allows max. 10 log messages per second per child process, it then begins throttling them (eventually making the child process start blocking on stderr). --HG-- branch : HEAD

Function typedefs now define them as functions, not function pointers. --HG-- branch : HEAD

Naming change for function typedefs. --HG-- branch : HEAD

Naming style changes, finally got tired of most of the typedefs. Also the previous enum -> macro change reverted so that we don't use the highest bit anymore, that's incompatible with old indexes so they will be rebuilt. --HG-- branch : HEAD

In case of internal errors in logging, exit() with FATAL_LOGERROR. --HG-- branch : HEAD

Added info_log_file setting and i_info() function to write to it. Default is the same as failure log. Currently only logged information is client logins. --HG-- branch : HEAD

Drop root privileges earlier. Close syslog more later in imap-master when forking new processes, so that any errors get logged. Make sure that all errors show up in log files - use specific exit status codes if we can't write to log file. Make sure imap and login processes always drop root privileges even if master process didn't ask for it for some reason. putenv() wasn't verified to succeed - luckily we never allowed large user given data there. --HG-- branch : HEAD

make sure failure handlers don't modify errno. --HG-- branch : HEAD

Initial revision --HG-- branch : HEAD