debug log - small but substantial change for 3.0.0 and fancy output

[Tomasz Wasilczyk]

Hi,

Currently, all calls to purple_debug_* should be terminated with LF
character. This can be handy in one awful situation: when we want to
print out the debug message in multiple calls to purple_debug_info. I
suggest changing this behavior: messages could be passed in their bare
form and LF (or other formatting data) could be added by logger
itself.

Advantages: I won't forget about trailing \n anymore; debug loggers
(like for our gtk frontend) will get debug messages clearly separated.

Another change is strictly about console output: there could be
additional switch "--debug=colored" to enable colors in bash console.
I've prepared an implementation for it. Cool, isn't it?

Please, take a look [1] and leave some comments. Is anyone against
committing it?

[1] https://dl.dropboxusercontent.com/u/5448886/pidgin-debug/debug-colored.patch

Tomek