Update Windows build files to Visual Studio 2015, add x64 platform, and adjust for libsrtp 2.0.x changes.

(These project files should work on older Visual Studio versions back to Visual Studio 2010 with minor adjustments.)
diff --git a/install-win.bat b/install-win.bat
index d95d6d9..02492bb 100644
--- a/install-win.bat
+++ b/install-win.bat
@@ -14,7 +14,7 @@
    exit /b 1
 )
 
-@for %%d in (include\srtp.h crypto\include\crypto.h Debug\srtp.lib Release\srtp.lib) do (
+@for %%d in (include\srtp.h Debug\srtp.lib Release\srtp.lib) do (
 	if not exist "%%d" (
 	   echo "%%d not found: are you in the right directory?"
 	   exit /b 1
@@ -22,10 +22,9 @@
 )
 
 mkdir %destdir%\include
-mkdir %destdir%\include\srtp
+mkdir %destdir%\include\srtp2
 mkdir %destdir%\lib
 
-copy include\*.h %destdir%\include\srtp
-copy crypto\include\*.h %destdir%\include\srtp
-copy Release\srtp.lib %destdir%\lib\srtp.lib
-copy Debug\srtp.lib %destdir%\lib\srtpd.lib
+copy include\srtp.h include\ekt.h %destdir%\include\srtp2
+copy Release\srtp2.lib %destdir%\lib\srtp2.lib
+copy Debug\srtp2.lib %destdir%\lib\srtp2d.lib