gnutls: fix spelling of GNUTLS_E_PREMATURE_TERMINATION

[Thomas Uhle]

fixes spelling mistake from commit #0eda57f2d3a6387c6b20ba66068cce22894f5690

Signed-off-by: Thomas Uhle <thomas.uhle at mailbox.tu-dresden.de>
---

--- openconnect/gnutls.c~	2014-04-16 19:06:26 +0200
+++ openconnect/gnutls.c	2014-04-16 19:09:13 +0200
@@ -116,7 +116,7 @@ int openconnect_SSL_read(struct openconn
  				vpn_progress(vpninfo, PRG_ERR, _("SSL read cancelled\n"));
  				return -EINTR;
  			}
-#ifdef GNUTLS_E_PERMATURE_TERMINATION
+#ifdef GNUTLS_E_PREMATURE_TERMINATION
  		} else if (done == GNUTLS_E_PREMATURE_TERMINATION) {
  			/* We've seen this with HTTP 1.0 responses followed by abrupt
  			   socket closure and no clean SSL shutdown.