Avoid crash on OS X: guarded fd exception

On OS X, a file descriptor that shows up as being of type "KQUEUE" in
lsof output is apparently created behind the scenes when starting a
thread. (Related to BSD kernel event queues: see man kqueue.) When we
re-exec ourselves on OS X, and then close all file descriptors >= 3,
closing such a KQUEUE fd causes a crash.

Guard against this by closing only regular files.

Change-Id: I5011bfbaed156b04248b6bddb2a1a58624bee3d4
5011bfbaed156b04248b6bddb2a1a58624bee3d4

sal/osl/unx/salinit.cxx

@@ -23,6 +23,7 @@
 #include <cassert>
 #include <limits>
 #include <unistd.h>
+#include <sys/stat.h>
 #endif
 
 #include "osl/process.h"
@@ -64,7 +65,9 @@ void sal_detail_initialize(int argc, char ** argv) {
     }
     assert(openMax >= 0 && openMax <= std::numeric_limits< int >::max());
     for (int fd = 3; fd < openMax; ++fd) {
-        close(fd);
+        struct stat s;
+        if (fstat(fd, &s) != -1 && S_ISREG(s.st_mode))
+            close(fd);
     }
 #endif
     sal_initGlobalTimer();