This attribute was set in log.c, but not exported to other
modules in log.h

This allows us to remove some unneccessary variable
initializations that were added in r6277.  I did
audioOutput_shout.c a bit differently, to avoid some
jumps.

before:
$ size src/mpd
text    data     bss     dec     hex filename
225546    4040   14600  244186   3b9da src/mpd

after:
$ size src/mpd
text    data     bss     dec     hex filename
224698    4040   14600  243338   3b68a src/mpd

git-svn-id: https://svn.musicpd.org/mpd/trunk@6821 09075e82-0dd4-0310-85a5-a0d7c8717e4f