add whitelist of error_logger handlers not to delete when error_logger_r...

This helps systools detect registered name clashes

Support pretty printing records found in a module at compile time

Support backend modules defining their own gen_event handler ID

Reject invalid format strings more aggressively

BUGFIX: Avoid overloading the LOG macro.

Also, adapt the rest of lager to use this bitmask as well.

Added node to metadata in parse transfrom

Add "SMTP Support" section to README.org

Unnecessary debug message

Fix custom formatter spec for lager_file_backend (version 2)

This also removes the dependency on the syntax_tools and compiler
applications, which interfered with lager's startup/shutdown order.

Use -include instead of -include_lib

As the include file is located in the same application, using
-include instead of -include_lib removes the need for the
code directory to be called "lager" or "lager-VSN".

Performance improvement in date formatting function.

The micro-benchmarks show up to 20x improvement, which further
reduces logging overhead.

Changed the messages sent to the backends to include metadata and separated formatting from the backend

Helps with pattern matching.

I didn't want the lager_log_message record being used across application
boundaries, this will insulate other applications from any changes to
the message type's internal structure.