Make compatible with Visual Studio 2015

Changes are identicall to facebookarchive#105

Author: davidcernat

Lib/LibStatic/CMakeLists.txt

@@ -17,7 +17,7 @@ IF(WIN32 AND NOT UNIX AND NOT MSYS)
 
 	IF(NOT ${CMAKE_GENERATOR} STREQUAL "MSYS Makefiles")
 
-		IF( MSVC10 OR MSVC11 OR MSVC12 )
+		IF( MSVC10 OR MSVC11 OR MSVC12 OR MSVC14 )
 			set_target_properties(RakNetLibStatic PROPERTIES STATIC_LIBRARY_FLAGS "/NODEFAULTLIB:\"LIBCD.lib LIBCMTD.lib MSVCRT.lib\"" )
 		ELSE()
 			set_target_properties(RakNetLibStatic PROPERTIES STATIC_LIBRARY_FLAGS "/NODEFAULTLIB:"LIBCD.lib LIBCMTD.lib MSVCRT.lib"" )

Source/CCRakNetSlidingWindow.cpp

@@ -22,7 +22,7 @@ static const CCTimeType SYN=10000;
 
 #include "MTUSize.h"
 #include <stdio.h>
-#include <math.h>
+#include <cmath>
 #include <stdlib.h>
 #include "RakAssert.h"
 #include "RakAlloca.h"