NEW: limit log files within 30 by deleting old files

Change-Id: I1bb5c827c7fb01d97b84a4a1bf3f905bb8e90448
(cherry picked from commit 065ef224357352851cbba2c0dcac131ea9acae82)

src/slic3r/GUI/GUI_App.hpp

@@ -26,6 +26,7 @@
 
 #define BBL_HAS_FIRST_PAGE          1
 #define STUDIO_INACTIVE_TIMEOUT     15*60*1000
+#define LOG_FILES_MAX_NUM           30
 
 class wxMenuItem;
 class wxMenuBar;