code,pal: Removes unused headers.

`<typeinfo>` and `<errno.h>` were unused in `seh.cpp`.
On FreeBSD, the `errno` macro was conflicting due to these
stale inclusions. The exact cause is still unknown that how
it is building on CI and only failing locally on clean FreeBSD 10.2
installation with Clang 3.5.

Fixes #1091.

Author: Peter Jas

src/pal/src/exception/seh.cpp

@@ -19,9 +19,7 @@ Module Name:
 
 --*/
 
-#include <typeinfo>
 #include "pal/thread.hpp"
-#include "signal.hpp"
 #include "pal/handleapi.hpp"
 #include "pal/seh.hpp"
 #include "pal/dbgmsg.h"
@@ -30,18 +28,19 @@ Module Name:
 #include "pal/init.h"
 #include "pal/process.h"
 #include "pal/malloc.hpp"
+#include "signal.hpp"
 
 #if HAVE_ALLOCA_H
 #include "alloca.h"
 #endif
 
-#include <errno.h>
-#include <string.h>
 #if HAVE_MACH_EXCEPTIONS
 #include "machexception.h"
 #else
 #include <signal.h>
 #endif
+
+#include <string.h>
 #include <unistd.h>
 #include <pthread.h>
 #include <stdlib.h>