Added log feature

Added "--log <filename>" option which writes all activity to specified
file.

src/main.c

@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include "gotty/options.h"
 #include "gotty/tty.h"
+#include "gotty/log.h"
 
 int main(int argc, char *argv[])
 {
@@ -34,9 +35,16 @@ int main(int argc, char *argv[])
     /* Configure output terminal */
     configure_stdout();
 
+    /* Install log exit handler */
+    atexit(&log_exit);
+
     /* Restore output terminal on exit */
     atexit(&restore_stdout);
 
+    /* Create log file */
+    if (option.log)
+        log_open(option.log_filename);
+
     /* Connect to tty device */
     if (option.no_autoconnect)
         status = connect_tty();
@@ -50,5 +58,8 @@ int main(int argc, char *argv[])
         }
     }
 
+    /* Close log */
+    log_close();
+
     return status;
 }