openssl: Add NPN crate feature

.travis.yml

@@ -5,7 +5,7 @@ os:
 env:
   global:
   - secure: J4i75AV4KMrU/UQrLIzzIh35Xix40Ki0uWjm8j05oxlXVl5aPU2zB30AemDne2QXYzkN4kRG/iRnNORE/8D0lF7YipQNSNxgfiBVoOEfj/NSogvI2BftYX9vlLZJUvt+s/nbE3xa/Pyge1IPv7itDYGO7SMe8RTSqitgqyfE2Eg=
-  - FEATURES="tlsv1_1 tlsv1_2 aes_xts"
+  - FEATURES="tlsv1_1 tlsv1_2 aes_xts npn"
 before_script:
 - openssl s_server -accept 15418 -www -cert openssl/test/cert.pem -key openssl/test/key.pem >/dev/null 2>&1 &
 script:

openssl/Cargo.toml

@@ -14,6 +14,7 @@ tlsv1_2 = ["openssl-sys/tlsv1_2"]
 tlsv1_1 = ["openssl-sys/tlsv1_1"]
 sslv2 = ["openssl-sys/sslv2"]
 aes_xts = ["openssl-sys/aes_xts"]
+npn = ["openssl-sys/npn"]
 
 [dependencies.openssl-sys]
 path = "../openssl-sys"