Performance tweak to the logging routines.

Performance tweak to the logging routines.

_osrfLogToFile() is no longer a variadic function.  We always sent it the
same format string, and there was no point in sending a variable-length
parameter list that never actually varied in length.

Now we send it a fixed-length parameter list -- and thereby avoid two
calls to vsnprintf() that had been hidden in the VA_LIST_TO_STRING macro.

Also: added doxygen-style comments to several of the functions.

M    src/libopensrf/log.c

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@1810 9efc2488-bf62-4759-914b-345cdb29e865