Performance/bug fix in media monitor ScanMediaType().

Symlinks to other places (like /Applications on OS X disk images) can cause
unwanted scanning of irrelevant directories and a big performance hit.
Even worse is symlinks which point to themselves, or a parent directory,
which recurse forever and blow the stack. If anyone really thinks that symlinks
should be used in file counts, we can revisit and add recursion limit rules?

mythtv/libs/libmythbase/mythmedia.cpp

@@ -261,6 +261,9 @@ bool MythMediaDevice::ScanMediaType(const QString &directory, ext_cnt_t &cnt)
         if (("." == fi.fileName()) || (".." == fi.fileName()))
             continue;
 
+        if (fi.isSymLink())
+            continue;
+
         if (fi.isDir())
         {
             ScanMediaType(fi.absoluteFilePath(), cnt);