build: export more openssl symbols on Windows

This exports even more openssl symbols when building
on Windows. SSL_set_fd is one example of added symbol.

PR-URL: nodejs#7576
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Roman Reiss <me@silverwind.io>

node.gyp

@@ -487,7 +487,8 @@
             'mkssldef_flags': [
               # Categories to export.
               '-CAES,BF,BIO,DES,DH,DSA,EC,ECDH,ECDSA,ENGINE,EVP,HMAC,MD4,MD5,'
-              'NEXTPROTONEG,PSK,RC2,RC4,RSA,SHA,SHA0,SHA1,SHA256,SHA512,TLSEXT',
+              'NEXTPROTONEG,PSK,RC2,RC4,RSA,SHA,SHA0,SHA1,SHA256,SHA512,SOCK,'
+              'STDIO,TLSEXT',
               # Defines.
               '-DWIN32',
               # Symbols to filter from the export list.