ECDH: Add Everest Curve25519 to VS project files

This being the first 3rdparty-contribution, we may want to consider the
structure of the project file generation scripts. Perhaps add small,
constribution-specific scripts to each directory in 3rdparty instead of adding
all constraints to generate_visualc_files.pl?
diff --git a/scripts/generate_visualc_files.pl b/scripts/generate_visualc_files.pl
index 5cfefe1..90ab609 100755
--- a/scripts/generate_visualc_files.pl
+++ b/scripts/generate_visualc_files.pl
@@ -38,7 +38,7 @@
 
 if ($include_crypto) {
   $include_directories = <<EOT;
-../../include;../../crypto/include\r
+../../include;../../crypto/include;../../crypto/3rdparty/everest/include/;../../crypto/3rdparty/everest/include/everest;../../crypto/3rdparty/everest/include/everest/vs2010;../../crypto/3rdparty/everest/include/everest/kremlib\r
 EOT
 }