cli: Move some declarations into `cli.h`

This will help to keep new CLIs clean from internal headers.

Change-Id: I3e5515ae5645fcdce56c13df1ff23de829bbbdb9
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/72989
diff --git a/include/cli.h b/include/cli.h
index 1ba442b..e9e512c 100644
--- a/include/cli.h
+++ b/include/cli.h
@@ -64,4 +64,10 @@
 
 int flashprog_classic_main(int argc, char *argv[]);
 
+extern enum flashprog_log_level verbose_screen;
+extern enum flashprog_log_level verbose_logfile;
+int open_logfile(const char * const filename);
+int close_logfile(void);
+void start_logging(void);
+
 #endif