Updated included headers to support compilation on Windows (using Visual C++)

- most of posix related functions and constants in unistd.h can be
  found in io.h in Visual C++
- introduced src/compat/msvc.h to adjust for compiler differences (and
  avoid updating code with #ifdef blocks for Windows support)
- removed some included headers that are not needed (both on Unix and
  Windows builds)

src/operators/inspect_file.cc

@@ -23,6 +23,10 @@
 #include "src/operators/operator.h"
 #include "src/utils/system.h"
 
+#ifdef WIN32
+#include "src/compat/msvc.h"
+#endif
+
 namespace modsecurity {
 namespace operators {
 

src/operators/rbl.cc

@@ -16,10 +16,15 @@
 #include "src/operators/rbl.h"
 
 #include <sys/types.h>
+#ifndef WIN32
 #include <sys/socket.h>
 #include <netdb.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
+#else
+#include <winsock2.h>
+#include <ws2tcpip.h>
+#endif
 
 #include <string>
 

src/operators/rbl.h

@@ -17,10 +17,14 @@
 #define SRC_OPERATORS_RBL_H_
 
 #include <sys/types.h>
+#ifndef WIN32
 #include <sys/socket.h>
 #include <netdb.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
+#else
+#include <winsock2.h>
+#endif
 
 #include <string>
 #include <memory>