[Evolution-hackers] another camel api addition

[Not Zed <notzed ximian com>]

Ok, this one doesn't affect any code directly, but is a new feature.

I've added a new camel debug interface, to extend the
camel_verbose_debug global variable one.

It lives in "camel-debug.h".

New api call:

bool camel_debug(const char *key);

Returns true if the debug specified by 'key' is activated.

key is in one of 3 forms:

module:submodule
 - fully specified key for debug, e.g. 'imap:folder' for imap folder
operations.

module
 - checks for debug on the whole module

:submodule
 - checks for debug on a certain submodule.  e.g. ':folder' for all
folder operations.

Note that the only one actually implemented in code so far is
'exception'.


The user specifies debug options using a comma-separated list of keys
which mimic the above, in a new environmental variable CAMEL_DEBUG.

e.g.
CAMEL_DEBUG=imap:folder,exception

Will turn on imap folder debug, and exception debug (although remember
imap:folder debug doesn't exist yet).

The special key 'all' will turn on all debug.

Note that CAMEL_VERBOSE_DEBUG=1 still works as it always did, and is
equivalent to turning on 'all' for any code using the new interface.

Currently specifying 'all' is about all thats useful, i suspect over
time as we're debugging stuff, for it to filter through the code, to
become more useful.

 !Z