Use correct file time for filesLoaded hash table keys

The keys were filenames *after* we called realpath, but the keys
were file times from *before* we called it, so they may have been
incorrect for symlinks.

Author: d-torrance

M2/Macaulay2/m2/startup.m2.in

@@ -60,7 +60,7 @@ if firstTime then (
 	 loadedFiles##loadedFiles = filepath;
 	 if notify then printerr("loaded ", filepath));
      tryLoad = (filename, filepath, loadfun, notify) -> if fileExists filepath then (
-	 filetime := fileTime filepath;
+	 filetime := fileTime realpath toAbsolutePath filepath;
 	 if notify then printerr("loading ", filename);
 	 ret := loadfun filepath;
 	 markLoaded(filepath, filetime, notify);