Improve log level documentation

Now, the documentation clearly states the purpose of each log level.
Also, the documentation for set_log_level is corrected:  libnitrokey
always prints to stderr.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 46549c6..1cfb7fd 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -167,7 +167,8 @@ pub fn set_debug(state: bool) {
 }
 
 /// Sets the log level for libnitrokey.  All log messages are written to the
-/// standard output or standard errror.
+/// standard error stream.  Setting the log level enables all log messages on
+/// the same or on a higher log level.
 pub fn set_log_level(level: LogLevel) {
     unsafe {
         nitrokey_sys::NK_set_debug_level(level.into());