Gets pe_utils.c to compile with VS2015. (#488)

* Visual Studio 2015 (_MSC_VER == 1900) defines the snprintf function, so avoid defining it in those cases.

* Adds missing include (for 'sprintf').

* Gets pe_utils.c to compile with VS2015.

libyara/modules/pe_utils.c

@@ -1,11 +1,20 @@
 
 
-#if !HAVE_TIMEGM
-
-#include <time.h>
+#include <stdio.h>
 
+#include <yara/mem.h>
 #include <yara/integers.h>
 
+#if defined(WIN32)
+#include <string.h>
+#define strncasecmp _strnicmp
+#define timegm _mkgmtime
+#endif
+
+#if !HAVE_TIMEGM && !defined(WIN32)
+
+#include <time.h>
+
 static int is_leap(
     unsigned int year)
 {