vtls: renamed sslgen.[ch] to vtls.[ch]

lib/Makefile.inc

lib/connect.c

lib/curl_ntlm_msgs.c

lib/curl_sasl.c

lib/easy.c

lib/formdata.c

lib/ftp.c

lib/getinfo.c

lib/http.c

lib/http_digest.c

lib/imap.c

lib/openldap.c

lib/pingpong.c

lib/pop3.c

lib/sendf.c

lib/share.c

lib/smtp.c

lib/ssh.c

lib/transfer.c

lib/url.c